No Biochemical Barriers: Difference between revisions

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== [[Comic Books]] ==

* Tenzil Kim and his fellow Bismollians from ''[[The Legion of Super Heroes]]'' can eat ''anything'', except certain materials he specifically can't use his power against.

* In ''[[~~Tom Strong (Comic Book)|~~Tom Strong]]'' #16, it's established that while unaltered humans can eat Devil's Footstool food, the opposite is ''not'' true. (With a few exceptions, such as coffee.)

* In ''[[Tom Strong]]'' #16, it's established that while unaltered humans can eat Devil's Footstool food, the opposite is ''not'' true. (With a few exceptions, such as coffee.)

* In the backmatter for the second volume of ''[[League of Extraordinary Gentlemen]]'', this is a problem for Alice of all people after she returns from [[Alice in Wonderland|Wonderland]] through the looking glass. Her whole body is reversed left-to-right, so her hair part is on the wrong side - as is her heart. Then, she mysteriously dies of malnutrition, despite eating normally for a while. It's not explained in the text, as Victorian science wouldn't be able to figure it out, but the science-minded reader might conclude that the reversal extended all the way down to the molecular level, and that Alice's amino acids were backwards compared to those in her food.

* ''Green Lantern''. The human Green Lanterns have problems getting good food at the Oan cafeteria. The chef just isn't that skilled.

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== [[Film]] ==

* Many films where aliens, particularly sentient ones, eat humans (humans being eaten by alien beasts can be explained by the alien eating things that act like prey without knowing that it's bad for the alien's health).

* The ''[[Men in Black (~~Film~~)|Men in Black]]'' films and cartoons imply that all alien immigrants and visitors to earth can eat (or appear to eat, in the case of the [[Mobile Suit Human]]-wearing Arquelliens) human food, although most of them ''need'' to in order to live as [[Muggles|ordinary humans]].

* The ''[[Men in Black (film)|Men in Black]]'' films and cartoons imply that all alien immigrants and visitors to earth can eat (or appear to eat, in the case of the [[Mobile Suit Human]]-wearing Arquelliens) human food, although most of them ''need'' to in order to live as [[Muggles|ordinary humans]].

* The aliens in [[District 9]] eat a lot of beef and pork, and have a craving for tinned cat food. Though, they also chew tires as if they were bubblegum, so their biology is somewhat different.

* In ''[[Alien Nation (TV)|Alien Nation]]'', the Newcomers are perfectly capable of eating earth food, with some variants. They prefer more exotic meats (such as beaver), which they eat raw as they can't absorb nutrients otherwise; they get drunk off spoiled milk; and the drug that drives the plot of the film {{spoiler|looks and tastes like dish soap to humans}}. They also dissolve in seawater and use arsenic flakes as a food seasoning. Justified in that they are a genetically modified life form.

* In ''[[Alien Nation (TV series)|Alien Nation]]'', the Newcomers are perfectly capable of eating earth food, with some variants. They prefer more exotic meats (such as beaver), which they eat raw as they can't absorb nutrients otherwise; they get drunk off spoiled milk; and the drug that drives the plot of the film {{spoiler|looks and tastes like dish soap to humans}}. They also dissolve in seawater and use arsenic flakes as a food seasoning. Justified in that they are a genetically modified life form.

* Averted in ''[[Avatar (~~Film~~)|Avatar]]'', in which the planet's atmosphere is deadly to humans.

* Averted in ''[[Avatar (film)|Avatar]]'', in which the planet's atmosphere is deadly to humans.

* Averted for comic effect in [[~~Galaxy Quest (Film)|~~Galaxy Quest]], when the actor that the aliens think is an alien is treated to food from his "native" planet... seaweed-like stuff and ''live bugs'' in a bowl of water. It also has the [[Only Sane Man]], Guy, pointing out that going out on the alien planet without checking its atmosphere first is insane. They do it anyway (and survive).

* Averted for comic effect in [[Galaxy Quest]], when the actor that the aliens think is an alien is treated to food from his "native" planet... seaweed-like stuff and ''live bugs'' in a bowl of water. It also has the [[Only Sane Man]], Guy, pointing out that going out on the alien planet without checking its atmosphere first is insane. They do it anyway (and survive).

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* ''~The Hitchhiker's Guide To The Galaxy~'' has approximately 85% of sentient races having a drink called a "gin and tonic" (or "jynnan tonnyx", or "jinond-o-nicks", or "gee-N'N-T'N-ix", or "chinanto-mnigs", or "tzjin-anthony-ks"...). However, all these drinks are radically different, ranging from a gin and tonic to ordinary water at slightly above room temperature to a drink that supposedly kills cows at a hundred paces. Yet they all have the same name, and were all named such before the races had discovered space travel. This may also apply to Ouisghian Zodahs.

** Also specifically averted, as Ford tells Arthur that things like nuts and berries native to alien planets may well kill you. (Or they may not, but there's normally no way to tell except to try them, so only try them when you're at the point of dying if you DON'T find something edible.)

* Averted in ''2061'' by [[Arthur C. Clarke ~~(Creator)~~]]. A spaceship lands on Europa, one of the crew is killed, and the corpse is eaten by a large water creature. Said creature promptly dies, because the biochemical differences means that human flesh is poisonous to it.

* Averted in ''2061'' by [[Arthur C. Clarke]]. A spaceship lands on Europa, one of the crew is killed, and the corpse is eaten by a large water creature. Said creature promptly dies, because the biochemical differences means that human flesh is poisonous to it.

* Averted in the ''My Teacher is an Alien'' series: when a human on a space ship full of thousands of species goes to the dining hall, a couple of crewmembers analyze his biochemistry and hunt through the menu/database for something that they're ''almost'' certain will not make him vomit or drop dead.

* Averted in [[Larry Niven]]'s ''[[Ring World]]'': the protagonist mentions that he once survived an attack by an alien beast because it stopped to swallow the chunk of him it had already ripped off and promptly curled up and died, poisoned by his biochemistry. And Justified in the case of those lifeforms that evolved from abandoned Slaver foodplanets, like Earth and Kzin.

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"Not a chance, Green-Eyes." }}

* Averted in ''[[Fallen Dragon]]'' by Peter F. Hamilton, where alien ecosystems are completely incompatible with human biochemistry -- meaning the first step in colonizing a new world is to kill all the native flora.

** Played straight in his ''[[~~The Nights Dawn Trilogy (Literature)|~~The Nights Dawn Trilogy]]'', where many exotic foodstuffs are imported from alien planets, and earth plants are genetically tweaked to grow on other worlds; the best alcoholic beverage in the Human Confederation is made from the water accumulated in the flowers of Norfolk roses. A short tale describes how some of the first scientists to land there, while inspecting the local flora, tasted said water. Norfolk was cleared for colonization days later as a result.

** Played straight in his ''[[The Nights Dawn Trilogy]]'', where many exotic foodstuffs are imported from alien planets, and earth plants are genetically tweaked to grow on other worlds; the best alcoholic beverage in the Human Confederation is made from the water accumulated in the flowers of Norfolk roses. A short tale describes how some of the first scientists to land there, while inspecting the local flora, tasted said water. Norfolk was cleared for colonization days later as a result.

* Apparently, anything in the universe they can get a hoof into is edible to the [[Animorphs ~~(Literature)~~|Andalites]]. They absorb nutrients, not consume them, so presumably they avoid anything they don't need/want. This deprives them of a sense of taste though, so [[Hilarity Ensues]] whenever they [[Sense Freak|morph into humans.]] Ax also complains at one point about accidentally eating snails when he grazes since as a herbivores it's probably quite disturbing to him that he just killed and ate an alien creature.

* Apparently, anything in the universe they can get a hoof into is edible to the [[Animorphs|Andalites]]. They absorb nutrients, not consume them, so presumably they avoid anything they don't need/want. This deprives them of a sense of taste though, so [[Hilarity Ensues]] whenever they [[Sense Freak|morph into humans.]] Ax also complains at one point about accidentally eating snails when he grazes since as a herbivores it's probably quite disturbing to him that he just killed and ate an alien creature.

** Similarly, Taxxons can apparently eat just about anything (or anyone). Also, Hork-Bajir are capable of eating the bark of Earth's trees.

* Averted in [[John Ringo]] and [[David Weber]]'s ''[[Prince Roger]]/Empire of Man'' series, where, while stuck on the alien planet, a good deal of effort is spent trying to find foods close enough that their nanites can adapt them to provide what they need.

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** This gets subverted in [[John Ringo]]'s latest book, [[Live Free Or Die]], where maple syrup is an incredibly potent alchohol-like substance for one of the alien races.

* Averting this trope is the whole premise of [[Larry Niven]]'s ''Destiny's Road,'' where human colonists populate a biochemically incompatible planet. People gain no sustenance from native life (and vice versa). They live on transplanted Earth animals and plants, but something different about the place means essential nutrients are missing, so humans must regularly consume something called "speckles" or go insane and die. The native life does not contain fat, or (key plot point) potassium (with the exception of a few plants). You CAN survive on the native life forms (at least for a lot longer than by starving) but you'll gradually lose all body fat, so makeup and source of "speckles" is a major plot point. This is used by a character trying to lose weight<ref>[[Science Marches On]] may not be kind to this character's plan. Modern food science is discovering that you can fool the metabolism like that for a short while, but humans eating filling but indigestible food acquires a '''terrible''' taste memory very quickly. This is why a bunch of Fat Substitutes failed in the late '90s</ref>, as you feel full, but your system can't process the food. You excrete everything and keep nothing--rapid weight loss happens then.

* Somewhat touched upon by [[Harry Turtledove]]'s ''[[Worldwar ~~(Literature)~~]]'' [[Alternate History]] series. The Race's biology and biochemistry are similar enough that they can live on Earth and eat some Earth biomatter with pretty much no problems. However, what would be slightly chilly to humans is beastly cold to them (apparently, their home planet is so hot that ice only exists in laboratories) and household spice ''ginger'' is so addictive to them it becomes their version of cocaine. It also triggers "heat" in their females.

* Somewhat touched upon by [[Harry Turtledove]]'s ''[[Worldwar]]'' [[Alternate History]] series. The Race's biology and biochemistry are similar enough that they can live on Earth and eat some Earth biomatter with pretty much no problems. However, what would be slightly chilly to humans is beastly cold to them (apparently, their home planet is so hot that ice only exists in laboratories) and household spice ''ginger'' is so addictive to them it becomes their version of cocaine. It also triggers "heat" in their females.

* Averted in [[Eric Flint]]'s ''Mother of Demons'', in which humans can eat ''nothing'' on the planet Ishtar but "childfeed," which is semidigested plant material regurgitated by large herbivorous lifeforms (normally to feed their offspring). Additionally, it turns out that {{spoiler|the meat or bodily fluids of every animal on the planet are deadly poisonous to humans--but then, it also works the other way around.}}

* In ''Chasm City'' by Alastair Reynolds, one human is tortured by being fed to a hamadryad (a giant snake-like alien) which swallows him whole and promptly dies due to terran proteins being lethally toxic to it. The victim is cut out of the creature's stomach, still alive if a little unhinged by the experience.

* Averted in ''[[The Mote in ~~Gods~~ Eye]]''. After a good deal of biochemical research, the Moties eventually come up with some local foods that the humans can eat. Moties find coffee about as lovely as torture, but they do like hot chocolate.

* Averted in ''[[The Mote in God's Eye]]''. After a good deal of biochemical research, the Moties eventually come up with some local foods that the humans can eat. Moties find coffee about as lovely as torture, but they do like hot chocolate.

** Don't forget the drop of machine oil in the cup!

* Specifically mentioned in David Gerrold's ''[[The War Against the Chtorr]]'' novels: the invading Chtorrans have absolutely no problem chowing down on Earth lifeforms, leading human scientists to speculate that the attackers were deliberately created/bred to be compatible. (Whether this is true or not is [[Vaporware|yet to be revealed]].)

* In the 1992 novel ''Murasaki'', written by several well-known science fiction authors, this trope is averted in an almost sad way. Humans discover the planet Murasaki and mount an expedition. The local life is almost completely poisonous to humans because they use a wider variety of amino acids. The natives, in an effort to make friends with the humans, find one life form that has some parts that are edible to us and present them in a feast. They are delicious. But they are also now extinct. Every last of the animals was harvested in order to provide the feast.

* Subverted in [[Terry Pratchett]]'s ''Strata'' where an important plot point is that the carnivorous Silver has a different biological makeup that makes it impossible for her to eat meat from a different planet. Being a predator, she will however turn into a ravenous badass killing beast which will still kill everyone in sight if her hunger gets the better of her.

* Also subverted in Pratchett's [[Discworld]] novel "[[Discworld ~~(Literature)~~/Moving Pictures|Moving Pictures]]".

* Also subverted in Pratchett's [[Discworld]] novel "[[Discworld/Moving Pictures|Moving Pictures]]".

{{quote| '''Troll''': I knows what they say about us trolls, but it not true! We made of rock. We don't eat humans! <br />

'''Other Troll''': Swallow. We don't swallow. }}

* Used somewhat in Allen Steele's ''Coyote''. A colony ship of humans going to a new, alien world doesn't know, while in orbit, if the planet has the right kind of soil(dextro versus levo amino acids may have been involved) to grow Earth crops; the colonists couldn't have survived on native food from the wrong kind of soil. They were lucky.

* Tully, the sole human in [[CJ Cherryh|C.J. Cherryh's]] ''Chanur Saga'', has no problem with Hani food.

* Tully, the sole human in [[C. J. Cherryh|C.J. Cherryh's]] ''Chanur Saga'', has no problem with Hani food.

** In the ''[[Foreigner (~~Literature~~)|Foreigner]]'' series humans must be very careful as to what atevi food they eat. Many "teas" and seasonings are deadly to them. The atevi can eat all human foods without problem, though human food is lacking in essential atevi vitamins, so an atevi can't survive on ''only'' human food.

** In the ''[[Foreigner (novel)|Foreigner]]'' series humans must be very careful as to what atevi food they eat. Many "teas" and seasonings are deadly to them. The atevi can eat all human foods without problem, though human food is lacking in essential atevi vitamins, so an atevi can't survive on ''only'' human food.

* It is mentioned in a ''[[Dragonriders of Pern]]'' novel that humans cannot eat any of the native Pern plants and can only eat the plants originally brought from Earth, but they they can eat the native animals.

** McCaffrey also averted this trope in ''Dinosaur Planet'', in which the exploration team heavily tests any local organism they consider using for food. Also, {{spoiler|the intelligent pterodactyls that were [[Transplanted Humans|transplanted from Earth]] to Ireta separate out any native fringe-organisms from their fishing nests and discard them as inedible.}}

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* The Apicians in the [[Cordwainer Smith]] short story "From Gustible's Planet" are capable of eating Earth food (and think it's delicious). This is specifically said to be unusual, though.

* In addition to the disease issue, this is also brought up in the ''[[Sector General]]'' novels. Specifically, the cafeteria at the hospital has a very wide selection of foods on the menu, with notations as to what foods can be safely eaten by what species. Occasional problems come when a diagnostician comes in for lunch after having a tape personality active for awhile, and as a result has to force himself to pick a meal that is suitable for his actual body rather than what his alternate personality thinks he is, and then force himself to eat what looks to be a highly unappetizing substance from the tape personality's perspective.

* The food of one planet is inedible to a native of another planet in ''[[~~The Madness Season (Literature)|~~The Madness Season]]''. In addition, the main character, a [[Voluntary Shapeshifting|shapeshifter]] is only able to transform into creatures native to the planet Earth.

* The food of one planet is inedible to a native of another planet in ''[[The Madness Season]]''. In addition, the main character, a [[Voluntary Shapeshifting|shapeshifter]] is only able to transform into creatures native to the planet Earth.

* This trope goes all the way back to the first [[Space Opera]], ''[[Skylark Series|The Skylark of Space]]''. Though the main characters are initially wary of eating Osnomian food, Seaton gives some Earth spices ([[Everybody Smokes|as well as cigarettes]]) to an Osnomian without being at all worried for the alien's health.

== [[Live Action TV]] ==

* ''[[~~Babylon Five|~~Babylon 5]]'' features several examples of characters consuming food from alien societies. Sometimes there's no problem, other times... Well, this is what happens when Centauri try human fast food: "It tastes ''so good'' going down. Coming back up, it's not so good." And just about ''everybody'' can (and does) eat [http://babylon5.wikia.com/wiki/Spoo#The_Other_Grey_Meat spoo]. Even pak'ma'ra, who are carrion-eaters with a strict religious-based dietary code.

* ''[[Babylon 5]]'' features several examples of characters consuming food from alien societies. Sometimes there's no problem, other times... Well, this is what happens when Centauri try human fast food: "It tastes ''so good'' going down. Coming back up, it's not so good." And just about ''everybody'' can (and does) eat [http://babylon5.wikia.com/wiki/Spoo#The_Other_Grey_Meat spoo]. Even pak'ma'ra, who are carrion-eaters with a strict religious-based dietary code.

** At one point G'Kar claims that every race has independently created their own version of Swedish Meatballs. According to the card game, even the Vorlons have one and it's apparently a sentient lifeform. Very much [[Played for Laughs]].

** When Londo Mollari asked what an item a salesman was offering, he said "Candy, only for carbon based life-forms who can metabolize sugar, otherwise it's decorative."

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** Another episode of TNG had Picard and Crusher stranded on an alien planet. Crusher was injured, and had Picard pick a random herb for its medicinal properties, which she could determine because its juices turned his skin yellow, and it tasted bitter (yes, the DOCTOR had Picard taste it before she knew what it was). This could have been justified as part of her medical training, except she says she knew of it because it was a folk remedy in her native Scotland.

** [[Deep Space Nine]] touched on this at least once. Sisko, annoyed by an assassination attempt made on the station, sits down with Gul Dukat and Weyoun (the official representative of the Dominion) with the bottle of poisoned kanar (Cardassian booze). As Sisko and Dukat argue, Weyoun knocks back a glass of the stuff, and exclaims, "Oh, that is ''quite'' toxic, isn't it?" Turns out Vorta are immune to most known poisons. This is probably due to the fact that the Founders of the Dominion pretty much genetically constructed the Vorta from the ground up to be their perfect servants.

** Averted in [[Star Trek Voyager]]. When Neelix and another person beam down to look for what the ship scans say are edible flora despite slightly harsh atmosphere (only slightly toxic, if a human (or Neelix) are exposed to it for too long could cause a rash and then after about three hours get seriously ill), they instead find nothing. The atmosphere actually also has amino acids and other nutrients in it that the local sentient but primitive live on, and it's slightly toxic to other species.

** Averted in [[Star Trek: Voyager]]. When Neelix and another person beam down to look for what the ship scans say are edible flora despite slightly harsh atmosphere (only slightly toxic, if a human (or Neelix) are exposed to it for too long could cause a rash and then after about three hours get seriously ill), they instead find nothing. The atmosphere actually also has amino acids and other nutrients in it that the local sentient but primitive live on, and it's slightly toxic to other species.

** Played amusingly straight in an early episode where a large portion of the crew beams down to a planet to forage for food. One crewman locates what appears to be an apple and is about ready to bite into it before Neelix explains that it's highly toxic and will cause all sorts of unpleasant reactions. This despite the fact that by this point Neelix has known of the existence of humanity for maybe a month and definitely doesn't have the medical knowledge required to know what would happen to human physiology if they ingest the fruit. He then goes on to recommend a less tasty but much more suitable plant instead...

** In TNG, it was revealed that the transporters have a "biofilter" that is capable of removing pathogens (but to look at it sardonically, it basically doesn’t ever work any time an episode is about bringing a plague onto the ship).

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== [[Video Games]] ==

* Justified in ''[[Sid ~~Meiers~~ Alpha Centauri]]'', where you have to research the appropriate technologies in order to harvest resources from xenofungus squares. This quote from an in-game character sums it up:

* Justified in ''[[Sid Meier's Alpha Centauri]]'', where you have to research the appropriate technologies in order to harvest resources from xenofungus squares. This quote from an in-game character sums it up:

{{quote| '''Deirdre''': Juicy ripe grenade fruits may look appealing, but a mouthful of highly toxic organonitrates will certainly change your mind in a hurry.}}

** Furthermore, although it's mostly [[All There in the Manual]], it's explicitly stated that although terrestrial plants take to Chiron like flies to honey (or perhaps more precisely vinegar) humans must wear oxygen masks and filter their water with ozone lest they die of nitrogen narcosis.

* Averted in ''[[Mass Effect]]''; turian, quarian and volus biology is such that they cannot eat the same food as most other species. Turians and quarians both [[Mirror Chemistry|require dextro-amino acids in their proteins]] and can't derive nutrients from levo-foods, and at best the food will pass right through, providing no nutrients, as opposed to humans, salarians and asari, who all use levo-amino acids. Volus, meanwhile, have an ammonia-based biochemistry, which is utterly incompatible with everyone else's.

** A human in the [[Expanded Universe]] got sick off alien food designed to resemble earth origin food. Whether this is due to biochemical barriers, or a lack of competence on the aliens' part is unclear.

** Subverted on Noveria. Most human foodstuffs will make turians deathly ill, but they can eat doughnuts with no adverse effect. Presumably because doughnuts have no nutritional value to any species. See also [[Rule of Funny]]; it's a turian [[Donut Mess ~~With~~ a Cop|rent-a-cop who makes the comment about craving them]]...

** Subverted on Noveria. Most human foodstuffs will make turians deathly ill, but they can eat doughnuts with no adverse effect. Presumably because doughnuts have no nutritional value to any species. See also [[Rule of Funny]]; it's a turian [[Donut Mess with a Cop|rent-a-cop who makes the comment about craving them]]...

** In the sequel, there's a [[Optional Sexual Encounter|romance]] path for either a turian or a quarian, depending on PC gender. {{spoiler|In the case of the Quarian Tali, she actually contracts a mild allergic reaction to the male PC (but it was worth in in her opinion), while with the Turian Garrus, a female PC is cautioned by the ship's doctor not to... ingest.}}

** Also in said sequel, one mission involves a group of Alliance soldiers that crashed on a planet and started eating the local plant and animal life. The food caused gradually increasing neurological damage in those who consumed it.

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** You can also overhear a conversation between a Turian salesman and Human customer at a restaurant, in which the Turian explains (And not for the first time, judging by the tone of voice), that you cannot mix spices with the wrong chirality in human cooking, because it will kill him if he eats it. Cut content [http://www.youtube.com/watch?v=mGKQhuDW6B4&feature=related here] shows the Turians don't make much in the way of booze and they are amazed at what wonderful alcoholic drinks they make. Most of the stuff Turians drink for booze stem from Quarians.

* Used in ''[[Sword of the Stars]]'': Humans, [[Lizard Folk|tarka]] and [[Bee People|hivers]] can all eat each others' foodstuffs with no ill effects (though non-hivers find hiver food terribly bland). Hiver biochemistry and taste organs are wired such that human spices and fermented goods (such as cheese) are near-narcotic to them (on the other hand, they have on reaction whatsoever to ethanol), and hiver warriors apparently eat garlic as a form of manhood test because the taste sensation makes it actually dangerous to them. Zuul are able to eat pretty much everything (or anyone) without any bad side effects, though being genetically modified this may be justified.

* Played straight in [[~~Borderlands (Video Game)|~~Borderlands]]. The occasional spit-roasted Skag seen at raider camps can be [[Hand Wave|Handwaved]] as the ill-educated locales (i.e. [[Acceptable Targets|Rednecks]]) not knowing any better, but then you find that there is industry devoted to producing canned Skag meat which is quite popular.

* Played straight in [[Borderlands]]. The occasional spit-roasted Skag seen at raider camps can be [[Hand Wave|Handwaved]] as the ill-educated locales (i.e. [[Acceptable Targets|Rednecks]]) not knowing any better, but then you find that there is industry devoted to producing canned Skag meat which is quite popular.

* Played straight with the Mothership Zeta DLC of Fallout 3. Throughout the exploration of the titular alien spaceship the Lone Wanderer finds numerous alien delicacies like squids and worms that when consumed restore your health with no obvious side effects, not to mention there is an alien equivalent to Stimpacks that heals you just as well. Though the game in general does function on what people of the 1950s '''thought''' a world after nuclear war would be like, so it is most likely also showing what people from that era thought aliens would be like.

* In Halo, every alien species thus far (except for the Huragok and Lekgolo, who eat sludge and metal, respectively) are capable of eating humans with no ill effects. Brutes, especially, consider humans very nice eating (at a [[Nightmare Fuel]] extent), and grunts, jackals, and drones will happily chow down on [[PO Ws]] and [[KI As]]. The first human to visit Sanghelios (the Elite homeworld) is served Sangheili food with no problem, although the, um, texture isn't very appetizing ("Who ate that before you?").

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== [[Web Comics]] ==

* The huge and scary [[Kaiju|People-Eating Poly-Sorbate Insectoid]] in ''[[The Inexplicable Adventures of Bob]]'' is perfectly capable of swallowing a man-sized creature whole, but cannot digest Earth life. Hence, a swallowed character can punch the critter's stomach lining until he is... forcefully regurgitated.

* In ''[[~~Freefall (Webcomic)|~~Freefall]]'', the incompatability of amino acids on Pfouts with terran biochemistry was the reason for Dr. Bowman's experiments with uplifting nonsapient species, in lieu of ''very'' expensive space travel and [[Terraforming]]. The Bowman's Wolf (including Florence) was to be a "proof of concept" test.

* In ''[[Freefall]]'', the incompatability of amino acids on Pfouts with terran biochemistry was the reason for Dr. Bowman's experiments with uplifting nonsapient species, in lieu of ''very'' expensive space travel and [[Terraforming]]. The Bowman's Wolf (including Florence) was to be a "proof of concept" test.

** Played with in regards to Sam's biochemestry; since he comes from a planet with a relatively benign climate that forced few selection-pressures on his species and lacked anything like the asteroid strike believed to kill off dinosaurs on Earth, his protein structure is surprisingly simple, and Deeee-licious to most Terran animals.

== [[Western Animation]] ==

* Averted in ''[[~~Ben 10 (Animation)|~~Ben 10]]'' of all things. Ben feeds an alien chocolate, and nearly kills him in the process. This particular alien was a pastiche of [[Superman]], thus making chocolate his ''[[Weaksauce Weakness|kryptonite]]'' and only ate it because Ben offered, and he didn't want to seem rude (though neither of them seemed to KNOW that this would happen).

* Averted in ''[[Ben 10]]'' of all things. Ben feeds an alien chocolate, and nearly kills him in the process. This particular alien was a pastiche of [[Superman]], thus making chocolate his ''[[Weaksauce Weakness|kryptonite]]'' and only ate it because Ben offered, and he didn't want to seem rude (though neither of them seemed to KNOW that this would happen).

* Completely averted in ''[[Invader Zim]]''. Water is caustic to the eponymous alien, and meat actually fuses to his flesh. He does attempt to build up a tolerance, but GIR, being a robot, can (and does) eat anything.

** There was one Earth food Zim discovered he ''could'' eat (to his own surprise) in the episode [[Exactly What It Says On the Tin|Zim Eats Waffles]], [[Lethal Chef|except the ones made by GIR]] because he put peanuts and ''soap'' in them.

** There was one Earth food Zim discovered he ''could'' eat (to his own surprise) in the episode [[Exactly What It Says on the Tin|Zim Eats Waffles]], [[Lethal Chef|except the ones made by GIR]] because he put peanuts and ''soap'' in them.

{{quote| ''"GIR, your waffles have sickened me! '''[[Large Ham|Fetch me the bucket!]]''' ''}}

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== [[Anime]] and [[Manga]] ==

* In ''[[~~Dragonball~~]] Z'', Goku apparently contracts a disease while on the planet Yardrat, weakening his heart and which would have eventually killed him. He's saved by a vaccine brought over from an alternate future where he ''did'' die. Of course, while Goku is an alien himself, the Saiyan biochemistry is identical to a human being's as far as [[Big Eater|nutrition]] and [[Half-Human Hybrid|reproduction]] are concerned.

* In ''[[Dragon Ball]] Z'', Goku apparently contracts a disease while on the planet Yardrat, weakening his heart and which would have eventually killed him. He's saved by a vaccine brought over from an alternate future where he ''did'' die. Of course, while Goku is an alien himself, the Saiyan biochemistry is identical to a human being's as far as [[Big Eater|nutrition]] and [[Half-Human Hybrid|reproduction]] are concerned.

* It is speculated that the parasite behind the [[Higurashi no Naku Koro Ni|Hinamizawa Syndrome]] actually came from another planet. Then again {{spoiler|the person who said that is also the one who wanted to turn it into a bio-weapon, so it's questionable how trustworthy this is}}.

* It is speculated that the parasite behind the [[Higurashi no Naku Koro ni|Hinamizawa Syndrome]] actually came from another planet. Then again {{spoiler|the person who said that is also the one who wanted to turn it into a bio-weapon, so it's questionable how trustworthy this is}}.

* ''[[Crossbone Gundam]]: Ghost'' has an alien microbe that the villains plan on releasing on Earth, which the heros are trying to prevent. The logic is that since the microbe has a completely alien biochemistry, nothing on Earth will be able to defend against it, and it will spread like wildfire and wipe out any life it comes across. This totally ignores the fact that the opposite should be equally as true: the microbe should be just as defenseless against Earth's microorganisms. Or, in the most likely case, absolutely nothing happens, and the alien microbe dies due to lack of its native environment.

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== [[Film]] ==

* The Facehuggers in the ''[[Alien (~~Film~~)|Alien]]'' films are somehow able to impregnate species (like humans and dogs) that would not have been encountered in the environment in which they evolved or by the species that engineered them (the backstory is unclear on which is the case) as long as it is warm-blooded and alive. This is [[Hand Wave|unsatisfactorily explained]] by claiming that it is capable of adapting itself to the DNA of the host and incorporate features of said host into the Chestburster it produces, but this does not account for how it is able to do so with a completely unknown species with a vastly different biology. If we suppose it was engineered rather than evolved, it seems likely that its creators would have designed it to target a specific species, because making it so adaptable that it could infest completely unknown species would surely mean that it could adapt to infest the species that created them. (Which, according to some sources, is exactly what happened...) As far as in-movie canon goes, ''Resurrection'' makes it clear that the Alien and host's DNA are somehow mingled, even in the host's own blood. Of course, that's still crazy from a biochemistry point-of-view (why would aliens even ''have'' DNA?), but at least they try to explain it.

* The Facehuggers in the ''[[Alien (franchise)|Alien]]'' films are somehow able to impregnate species (like humans and dogs) that would not have been encountered in the environment in which they evolved or by the species that engineered them (the backstory is unclear on which is the case) as long as it is warm-blooded and alive. This is [[Hand Wave|unsatisfactorily explained]] by claiming that it is capable of adapting itself to the DNA of the host and incorporate features of said host into the Chestburster it produces, but this does not account for how it is able to do so with a completely unknown species with a vastly different biology. If we suppose it was engineered rather than evolved, it seems likely that its creators would have designed it to target a specific species, because making it so adaptable that it could infest completely unknown species would surely mean that it could adapt to infest the species that created them. (Which, according to some sources, is exactly what happened...) As far as in-movie canon goes, ''Resurrection'' makes it clear that the Alien and host's DNA are somehow mingled, even in the host's own blood. Of course, that's still crazy from a biochemistry point-of-view (why would aliens even ''have'' DNA?), but at least they try to explain it.

** Somewhat justified by a suggestion that the Xenomorphs were created as either a bioweapon or a terraforming construct (which is basically the same thing, when you come down to it). Step 1 of any biosphere replacement is going to be getting rid of the existing biosphere, and my aren't these efficient at slaughtering things... This idea presupposes that a simple, but non-obvious, kill switch exists in the Xenomorph biology allowing some easy-to-handle chemical to kill them all. Now imagine a strain that mutates so that it doesn't WORK any more...

== [[Literature]] ==

* In [[HG Wells]]' original ''[[War of the Worlds]]'' the Martians are killed off by a terrestrial microbe within several weeks of their arrival. This is almost a reversal of the trope, as it's rather explicitly stated that the aliens are ''more'' vulnerable to Earth microbes than humans, due to not having evolved and adapted alongside them; this is based upon the outbreaks that can occur when two previously isolated human cultures begin interacting and exchanging diseases, unintentionally or otherwise. Of course, this is because [[Science Marches On]]; the very idea of viral transmittance was new when the book was first written.

* In [[H. G. Wells]]' original ''[[War of the Worlds]]'' the Martians are killed off by a terrestrial microbe within several weeks of their arrival. This is almost a reversal of the trope, as it's rather explicitly stated that the aliens are ''more'' vulnerable to Earth microbes than humans, due to not having evolved and adapted alongside them; this is based upon the outbreaks that can occur when two previously isolated human cultures begin interacting and exchanging diseases, unintentionally or otherwise. Of course, this is because [[Science Marches On]]; the very idea of viral transmittance was new when the book was first written.

** ''[[War of the Worlds]]'' manages to hit the trifecta on this. In addition to the above virus example, the Martians are also capable of breathing Earth's atmosphere (to say nothing of the pressure. The only effect is that the higher concentration of oxygen invigorates them!) and "feed" (having "given up their digestive systems") by injecting themselves with human blood. Oh how science has marched on.

** Possibly averted in explaining why the Martians did not do to us as was done unto them: "Either there are no bacteria on Mars, or else Martian science eliminated them long ago." Wells allowed for the possibility that the Martians had created - and by extension adapted to - a totally germ-free environment and thus left themselves vulnerable to essentially everything. Earthly bacteria are amazingly resilient and resourceful under evolutionary pressure; it's hard not to imagine them finding ''something'' about a Martian they could get their flagella into.

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** Also averted in the ''[[Ring World]]'' books, in which inter-species sex (called ''rishathra'') is common, and it is explained that STDs aren't an issue. Disease transmission would be a little more plausible in this case than in most of the other examples, because {{spoiler|the humanoid inhabitants of the Ringworld are all distantly related to each other, and to Earthlings as well}}.

** [[Science Marches On|Apparently nobody had told Niven]] that new diseases could evolve from common soil bacteria, when he first introduced ''rishathra'' to the Ringworld's cultures. Until ''The Ringworld Throne'', he'd claimed the {{spoiler|Pak}} simply didn't put any pathogens there, V.D. included.

* In [[Arthur C. Clarke ~~(Creator)~~]]'s ''Before Eden'', astronauts discover lithovore slime-like life on Venus... only to wipe it out by inadvertently introducing pathogenic microorganisms from Earth.

* In [[Arthur C. Clarke]]'s ''Before Eden'', astronauts discover lithovore slime-like life on Venus... only to wipe it out by inadvertently introducing pathogenic microorganisms from Earth.

* The [[Lois McMaster Bujold|Vorkosigan Saga]] again: the notorious and disgusting worm plague of Sergyar. "It wasn't all that lethal, as plagues go."

* In the Ender's Game ''Speaker for the Dead'' trilogy the humans and their crops are infected by a virus, the Descolada, on the alien planet. This trope is averted by the facts that {{spoiler|the Descolada was engineered to specifically be able to adapt to different genetic codes, and that the virus may be semi-intelligent itself}}.

* In the ''[[~~Honor Harrington (Literature)|~~Honor Harrington]]'' series, this is part of the backstory for Manticore -- a few years after the colonists arrived, one of the local microbes crossed the species barrier and killed a substantial portion of the colonists. Somewhat justified in that one of the things that made Manticore inviting to colonize was how similar its biochemistry was to Earth's. Also, the original colonists' desire to maintain control while bringing in replacements for everybody who died is how Manticore ended up with a feudal system of government.

* In the ''[[Honor Harrington]]'' series, this is part of the backstory for Manticore -- a few years after the colonists arrived, one of the local microbes crossed the species barrier and killed a substantial portion of the colonists. Somewhat justified in that one of the things that made Manticore inviting to colonize was how similar its biochemistry was to Earth's. Also, the original colonists' desire to maintain control while bringing in replacements for everybody who died is how Manticore ended up with a feudal system of government.

** In the same universe, the capital planet of the Anderman Empire had a native microbe that was harmless to humans but ''ate chlorophyll''. The colony was slowly starving because of crop failures, when super-rich mercenary commander Gustav Anderman came along and paid for the expensive genetic engineering to make resistant plants, in exchange for being made emperor.

** Weber averts this again with the planet Grayson, a [[Death World]] full of heavy metals which forces them to do all their agriculture either under protective domes or on orbital farms.

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* Not exactly a disease, but in Silent Dances the main character avoids getting bug bites on the alien planet because the bugs can't handle her alien chemistry. On the other hand, she has no trouble eating most of the plants and animals on that planet for food...

* Averted in the Corean Chronicles for good reason. Virtually all of the native fauna and flora were less animals and plants than rocks and gas interwoven with energy; the necessary jump from silicon- to carbon-based lifeforms or vice versa would be a major barrier.

* In one ''[[~~Animorphs (Literature)|~~Animorphs]]'' book, Ax catches a disease. All of the human Animorphs but Cassie come down with apparently the same disease, which manifests as the flu in humans (though it's much more potentially ''fatal'' to Ax.) Worse, the disease seems to affect everyone ''even in morph'', including [[Shapeshifter Mode Lock|Tobias]], who spends very little time in human form.

* In one ''[[Animorphs]]'' book, Ax catches a disease. All of the human Animorphs but Cassie come down with apparently the same disease, which manifests as the flu in humans (though it's much more potentially ''fatal'' to Ax.) Worse, the disease seems to affect everyone ''even in morph'', including [[Shapeshifter Mode Lock|Tobias]], who spends very little time in human form.

* In ''[[Lucky Starr|David Starr, Space Ranger]]'', a series of poisonings occurs in people who ate Mars grown food. A (human) Martian scientist says it could have been a poisoning by the local bacteria. {{spoiler|Subverted later, when it turns out he was the [[Big Bad]] and was telling a deliberate lie.}}

== [[Live Action TV]] ==

* ''[[~~Babylon Five|~~Babylon 5]]'' had the Markab people fall victim to a universally fatal plague to which humans turned out to be completely immune, as it acted on a type of nerve cell that humans don't have. The Pak'ma'ra, however, turned out to be similar enough that it also affected them, though less severely. In fact, that similarity allowed Dr Franklin to figure out how to cure the disease - {{spoiler|too late to save the Markab}}.

* ''[[Babylon 5]]'' had the Markab people fall victim to a universally fatal plague to which humans turned out to be completely immune, as it acted on a type of nerve cell that humans don't have. The Pak'ma'ra, however, turned out to be similar enough that it also affected them, though less severely. In fact, that similarity allowed Dr Franklin to figure out how to cure the disease - {{spoiler|too late to save the Markab}}.

* In an episode of ''[[Stargate SG-1]]'', the local alien population of a planet are falling ill after the arrival of the main team. As the good guys desperately try to find a cure, General Hammond [[Lampshade Hanging|points out that they're lucky they mostly deal with human civilizations who have the same diseases as Earth do and that's it's a small miracle they haven't run into a problem like this before]]. The episode was ultimately an aversion, since it turned out that the illness wasn't caused by a disease.

** The Goa'uld are a race of parasitic worms that evolved on some distant planet, but seem to be capable of infecting every sentient race they come into contact with, without any discernible difficulty. They supposedly need to acquire the genetic code from a species they're going to infest and apparently do this via sex, which is...[[Nightmare Fuel|odd]], at least the first time. Also, the Jaffa were initially created to allow larval Goa'uld time to adjust to human hosts. (Prior to the Jaffa, many more Goa'uld died of rejection sickness.) The Goa'uld still can't parasitize some species, such as the Retou. It's also explicitly noted a couple times that some species or human populations are resistant or immune to Goa'uld infestation, but the Goa'uld make a habit of wiping them out.

* A ''[[Doctor Who]]'' episode had a human stung by the venomous tongue of a Silurian warrior, and begin to mutate. This trope is simultaneously played straight (it does affect him), subverted (the Silurian doesn't understand why he doesn't just die) and partially justified (Silurians and humans are both technically earthlings; they are just separated by millions of years of evolution).

** [[Doctor Who/Recap/S32 E10 The Girl Who Waited|The Girl Who Waited]] plays with this; the 'One Day Plague' only affects species with two hearts, so Time Lords and Apalapucians are at risk but humans are fine. Also, when Amy is trapped in a quarantine facility, the Doctor instructs her not to accept any medicine from the robotic staff; they can't comprehend that she's a different species to the rest of the inhabitants and any medicine they give her would be lethal.

* ''[[Star Trek Enterprise]]'' had an episode where a disease that was apparently a universal infector was used as a sociology experiment by an alien race that had surpassed physical existence -- they wanted to see what cultures would do if infected by an incurable airborne alien virus that killed quickly.

* ''[[Star Trek: Enterprise]]'' had an episode where a disease that was apparently a universal infector was used as a sociology experiment by an alien race that had surpassed physical existence -- they wanted to see what cultures would do if infected by an incurable airborne alien virus that killed quickly.

** The Star Trek novel ''Uhura's Song'' was all ''about'' finding the cure for an epidemic striking both humans and the catlike Eeiauoans, complicated (among other factors) by the fact that nobody on the planet that should hold the solution recognized its symptoms.

** The [[Star Trek ~~the~~ Original Series]] novel ''The IDIC Epidemic'' concerned a highly virulent and rapidly mutating disease that infected everyone living on a mixed-species treaty world. Originally a Klingon disease, it would affect everyone with similar blood chemistry (iron-based, copper-based, silicon-based), and leap from one blood chemistry to another via mixed-species children. In the end, Romulans (copper-based blood) were immune, and the Klingons (iron-based blood) had an ample supply of the cure, and mass inoculations saved the day.

** The [[Star Trek: The Original Series]] novel ''The IDIC Epidemic'' concerned a highly virulent and rapidly mutating disease that infected everyone living on a mixed-species treaty world. Originally a Klingon disease, it would affect everyone with similar blood chemistry (iron-based, copper-based, silicon-based), and leap from one blood chemistry to another via mixed-species children. In the end, Romulans (copper-based blood) were immune, and the Klingons (iron-based blood) had an ample supply of the cure, and mass inoculations saved the day.

* Averted in an episode of ''[[Battlestar Galactica]]''. The fleet stumbles across a Cylon basestar where all the Cylons on board are either dead or dying. It turns out that they've contracted a disease that humans became immune to millennia before due to {{spoiler|a probe from an Earth that had been populated by Cylons (the Thirteenth Tribe of Kobol). So in reality they contracted it from an earlier form of themselves}}.

** Unfortunately played straight when {{spoiler|the fleet reaches a second planet they dub Earth. Yes, it's our Earth, and humans have magically evolved there too. However, that's the ''least'' of the problems both scientific and dramatic with the finale...}}

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== [[Video Games]] ==

* In ''[[~~War Craft~~]] III'' and ''[[World of Warcraft]]'', although the Plague of Undeath created by the Lich King only affects humans and not any of the other intelligent species in the game universe, it still has mutagenic effects on plant and animal life. Probably because it's [[A Wizard Did It|magic]] and was made to prepare the land for undead invasion. In at least one quest it's explicitly stated to affect some other races, but not fully as intended; one quest involves getting bones from Murlocs that were turned into undead by the plague... but weren't robbed of their free will by it as humans would be.

* In ''[[Warcraft]] III'' and ''[[World of Warcraft]]'', although the Plague of Undeath created by the Lich King only affects humans and not any of the other intelligent species in the game universe, it still has mutagenic effects on plant and animal life. Probably because it's [[A Wizard Did It|magic]] and was made to prepare the land for undead invasion. In at least one quest it's explicitly stated to affect some other races, but not fully as intended; one quest involves getting bones from Murlocs that were turned into undead by the plague... but weren't robbed of their free will by it as humans would be.

** ''Warcraft'' also has [[Half Human Hybrids]], despite diseases apparently not translating well among species on the same planet. For example, Garona Halforcen who is half orc and half DRAENEI. Yup, alien parents from different planets. And then she had a son with MEDIVH, who is, biologically, pretty much human. So that's 3 species from 3 different planets who are all compatible with one another. Draenei and Orcs in particular are interesting, since their hybrids are clearly still fertile.

** When the Lich King first came to Northrend, he had difficulty fighting the Nerubians because they couldn't be infected and killed directly by the plague, but they weren't immune to the Scourge's Necromancy, so once some of them got killed by non disease means, they were able to be resurrected as undead slaves.

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== [[Web Comics]] ==

* Not disease, but medicine - ''[[~~Schlock Mercenary (Webcomic)|~~Schlock Mercenary]]'' averts this nicely by having characters have med-kits in their [[Tank Goodness|tanks]] specific to their species. These so far have not worked on other species, though there haven't (yet) been any incidences of adverse effects. Medical nanites are more-or-less universal, however.

* Not disease, but medicine - ''[[Schlock Mercenary]]'' averts this nicely by having characters have med-kits in their [[Tank Goodness|tanks]] specific to their species. These so far have not worked on other species, though there haven't (yet) been any incidences of adverse effects. Medical nanites are more-or-less universal, however.

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== [[Anime]] ==

* The planet Namek in ''[[~~Dragonball~~]] Z'' has a ''green sky''. That alone should point out the differences in composition with Earth's atmosphere, but the humans that visit this planet, and the Namek natives that visit Earth (and the multitude of other aliens from many different worlds that congregate on either planet) have no problem breathing in it or even fighting at full strength.

* The planet Namek in ''[[Dragon Ball]] Z'' has a ''green sky''. That alone should point out the differences in composition with Earth's atmosphere, but the humans that visit this planet, and the Namek natives that visit Earth (and the multitude of other aliens from many different worlds that congregate on either planet) have no problem breathing in it or even fighting at full strength.

** There's also a scene that [[Lampshade|lampshades]] this, where Bulma begins analyzing the atmosphere from inside their ship to see if it's breathable - only to look up and see that Gohan and Krillin are already outside.

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** Gravity gets a similar minor mention, in that humans who grew up on high-gravity worlds tended to be [[Heavyworlder|stocky]]. Otherwise it really doesn't come up.

** The EU from the novels goes a bit more in depth into this with the Gand (Technically two species). Group one of the Gand must breathe methane or they will enter a coma state. Group two no longer needs to breathe. Then there's the case of the Givin, a race that evolved on a [[Death World|planet with a horrific environment]], including massive gravity shifts caused by a destabilized moon. The Givin have an exoskeleton that allows them to survive in vacuum for short periods (Their planet would have its atmosphere shredded on a regular basis) and an amazing capacity for mathematics that helped them to predict when these gravity shifts would occur.

* Most of the aliens in the ''[[Men in Black (~~Film~~)|Men in Black]]'' films and [[Men in Black (~~Animation~~)|the cartoon]] get along fine without special respirators, although there are exceptions: one species risked premature aging in earth's atmosphere, while "Atlantis" (actually a [[Ancient Astronauts|sunken space ship]]) is a posh resort for (salt)water-breathing aliens. When Agent Jay is surprised at the fish-like aliens, Agent Kay [[Lampshade Hanging|lampshades]] this with "You think ''all'' aliens breathe oxygen?"

* Most of the aliens in the ''[[Men in Black (film)|Men in Black]]'' films and [[Men in Black (animation)|the cartoon]] get along fine without special respirators, although there are exceptions: one species risked premature aging in earth's atmosphere, while "Atlantis" (actually a [[Ancient Astronauts|sunken space ship]]) is a posh resort for (salt)water-breathing aliens. When Agent Jay is surprised at the fish-like aliens, Agent Kay [[Lampshade Hanging|lampshades]] this with "You think ''all'' aliens breathe oxygen?"

* [[Lampshade Hanging|Lampshaded]] and played hilariously straight in ''[[~~Galaxy Quest (Film)|~~Galaxy Quest]]'', when [[Cloudcuckoolander|Tech Sargent Chen]] opens the door of the ship while it's on an alien planet:

* [[Lampshade Hanging|Lampshaded]] and played hilariously straight in ''[[Galaxy Quest]]'', when [[Cloudcuckoolander|Tech Sargent Chen]] opens the door of the ship while it's on an alien planet:

{{quote| [[Genre Savvy|Guy]]: What're you doing! We're on an alien planet! Is there AIR? You don't know!<br />

Chen: (sniffing a few times) Seems okay. }}

* Present ''and'' subverted (and generally just plain [[You Fail Biology Forever|screwed up]]) in M. Night Shyamalan's ''Signs''. Aliens are seen walking around on Earth apparently sans any kind of protection whatsoever, but then turn out to be fatally allergic to water. ([[Fridge Logic|But let's not go into why hydrophobic aliens would decide to invade a planet 75% covered with water, nor how they managed to run through a misty cornfield at night]].)

* Partly averted in ''[[Avatar (~~Film~~)|Avatar]]''. Although the atmosphere is primarily oxygen/nitrogen (albeit denser), humans can not breathe it without filters due to the presence of lethal levels of carbon dioxide and hydrogen sulphide.

* Partly averted in ''[[Avatar (film)|Avatar]]''. Although the atmosphere is primarily oxygen/nitrogen (albeit denser), humans can not breathe it without filters due to the presence of lethal levels of carbon dioxide and hydrogen sulphide.

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== [[Live Action TV]] ==

* ''[[Star Trek]]'' is a frequent offender here. Given that the majority of the crews found aboard the ships the various series center around are human, it is reasonable to assume that the air they breathe is adapted to human physiology. Other oxygen-breathing species are almost never shown to find the pressure, temperature or the (presumable) presence of nitrogen and water vapour bothersome. The Benzites are the only race that's been described as needing something other than oxygen/nitrogen. It's possible the Breen count too, since those refrigeration suits aren't needed, as well as the Tholians, who naturally live in temperatures of at least 450 Kelvin (177 Celsius). This is given a [[Hand Wave]] by an episode of ''[[Star Trek ~~the~~ Next Generation]]'', which explains that most of the species in the Alpha Quadrant did in fact descend from the [[Precursors]], who scattered their genetic code across thousands of worlds, apparently [[Genre Savvy]] enough to know that their own society would inevitably [[And Man Grew Proud|grow proud]]. This goes some way to explaining why [[Rubber Forehead Aliens]] tolerate nitrogen/oxygen atmospheres, as well as other forms of alien/human... [[Half-Human Hybrid|interaction]].

* ''[[Star Trek]]'' is a frequent offender here. Given that the majority of the crews found aboard the ships the various series center around are human, it is reasonable to assume that the air they breathe is adapted to human physiology. Other oxygen-breathing species are almost never shown to find the pressure, temperature or the (presumable) presence of nitrogen and water vapour bothersome. The Benzites are the only race that's been described as needing something other than oxygen/nitrogen. It's possible the Breen count too, since those refrigeration suits aren't needed, as well as the Tholians, who naturally live in temperatures of at least 450 Kelvin (177 Celsius). This is given a [[Hand Wave]] by an episode of ''[[Star Trek: The Next Generation]]'', which explains that most of the species in the Alpha Quadrant did in fact descend from the [[Precursors]], who scattered their genetic code across thousands of worlds, apparently [[Genre Savvy]] enough to know that their own society would inevitably [[And Man Grew Proud|grow proud]]. This goes some way to explaining why [[Rubber Forehead Aliens]] tolerate nitrogen/oxygen atmospheres, as well as other forms of alien/human... [[Half-Human Hybrid|interaction]].

** There was a nice moment in a ''Deep Space 9'' episode that seemed to acknowledge this, where Garak, a Cardassian, comments that the environmental settings on the eponymous station, adapted to Bajoran/human norms from their Cardassian originals, are uncomfortable to him - "the temperature is always too cold, the lights are always too bright". So even amongst ''[[Star Trek]]'''s rubber forehead brigade there are still variations in environmental tolerance.

** A plot point of the TOS episode ''Amok Time'' is that Vulcan's atmosphere contains less oxygen than humans are used to. Also, when afflicted with rapid aging in "The Deadly Years", Spock found it more difficult to tolerate the (for Vulcans) cold temperature of the ship environment. Presumably, he normally just puts up with the discomfort.

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* Justified in ''[[Stargate SG-1]]''. As Carter points out, you don't make easy travel to planets that are going to kill you if you go there. Also subverted several times when they do run across lethal atmospheres, usually caused by some kind of disaster like a volcano. In one case it was a radically different form of life terraforming the planet. They always send through a robot probe before going to an unknown planet.

** Also Justified because the Ancients had the same or very similar chemical composition as modern humans, and deliberately built their Stargates on planets they could inhabit in the Milky Way.

* Averted in ''[[~~Babylon Five|~~Babylon 5]]'' in that there are sections of the station sealed off for species that breathe atmospheres other than the oxy-nitrogen standard that seems to be common among the humanoid races. Some of these zones were mild enough that humans could enter them with just respirators, while others (never seen on screen) were apparently nasty enough to require full pressure suits. This difference is mostly informal, since except for the encounter suite-wearing Gaim and Vorlons ({{spoiler|the latter don't actually need them}}) and whatever Na'grath is supposed to be, any alien we see on Babylon 5 is effortlessly capable of surviving in earth-like atmospheric conditions.

* Averted in ''[[Babylon 5]]'' in that there are sections of the station sealed off for species that breathe atmospheres other than the oxy-nitrogen standard that seems to be common among the humanoid races. Some of these zones were mild enough that humans could enter them with just respirators, while others (never seen on screen) were apparently nasty enough to require full pressure suits. This difference is mostly informal, since except for the encounter suite-wearing Gaim and Vorlons ({{spoiler|the latter don't actually need them}}) and whatever Na'grath is supposed to be, any alien we see on Babylon 5 is effortlessly capable of surviving in earth-like atmospheric conditions.

* In ''[[UFO]]'' the aliens have the technology to [[Human Resources|adapt human organs to replace their own]], yet wear spacesuits as exposure to the Earth's atmosphere will kill them.

* ''[[~~Farscape (TV)|~~Farscape]]'' usually played this trope straight in all its incarnations but the atmosphere issue is subverted in one episode. In "Relativity" the alien mercenaries employed by Xhalax are used to much less air pressure so they have difficulty keeping up with her.

* ''[[Farscape]]'' usually played this trope straight in all its incarnations but the atmosphere issue is subverted in one episode. In "Relativity" the alien mercenaries employed by Xhalax are used to much less air pressure so they have difficulty keeping up with her.

* ''[[Power Rangers]]'' as a whole. Not sure whether the ranger's armor acts as a protective gear (surely it does in ''[[Power Rangers in Space]]''). But anyway, humans, [[Human Aliens]] good guys and Dark Specter's forces can breath on each other's planets. Oh, and apparently you can breath on Moon, and it has the same gravity as Earth.

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* Averted with the Grunts of ''[[Halo]]''. The massive suits and rebreathers they wear provide them with the methane atmosphere they require. All the other species seem to share in being adapted to the same atmospheric conditions as humans, which [[Fridge Brilliance|makes sense]] since most of the other sentient species were specifically preserved by the Forerunners, who lived on Earth-like planets. It's also implied [[All There in the Manual|supplemental material]] that Grunts may have evolved to breathe methane after they wrecked the atmosphere of their planet with oveindustrialization.

* Averted in ''[[Pikmin]]''. It's stated several times that the atmosphere of the planet Olimar gets stranded on contains a large amount of oxygen, which is highly toxic to his species. This is also why he has to repair his ship in thirty days, as this is how long he has before his suit's life support runs out.

* Averted in the ''[[Sid ~~Meiers~~ Alpha Centauri]]: Alien Crossfire'' expansion pack - Progenitor and human biological needs are so different that they cannot coexist in colonies together. In game terms, what this means is that when a human faction captures a Progenitor colony (or vice versa), the colony is depopulated to 1 population, and a number of colony pods (based on the population of the colony) are generated, representing the displaced population.

* Averted in the ''[[Sid Meier's Alpha Centauri]]: Alien Crossfire'' expansion pack - Progenitor and human biological needs are so different that they cannot coexist in colonies together. In game terms, what this means is that when a human faction captures a Progenitor colony (or vice versa), the colony is depopulated to 1 population, and a number of colony pods (based on the population of the colony) are generated, representing the displaced population.

** Also [[All There in the Manual|there in the manual]] for the game: the atmosphere of Planet is also nitrogen/oxygen, but the proportion of nitrogen is 90% instead of 78%, and the atmosphere overall is thicker so that while the partial pressure of oxygen is within acceptable limits, the amount of nitrogen you'd have to breathe in would give you nitrogen narcosis. Settlers are mentioned wearing special masks at minimum, and your soldiers are depicted wearing what appear to be pressure helmets. The tie-in novels mentioned that it was possible to go without a mask for short periods of time, so Deirdre made quite an impact on another faction by emerging from her vehicle, unmasked and smiling.

* Averted in the ''[[Metroid]]'' series: after the Chozo took the infant Samus Aran under their care, they subjected her to a carefully designed series of transgenic modifications with Chozo DNA, so she could merely ''survive'' in the unbelievably hostile atmosphere, and pressure, of Zebes. Even then, many parts of Zebes, to say nothing of other planets, are impassable to her without the Power Suit's environmental protections.

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* Cybertron in ''[[Transformers]]'' is shown to be equally hospitable to humans, various aliens, and robots with no need to breathe. This is despite there being no visible atmosphere in most of its depictions.

** It is also the [[Transforming Mecha|altmode]] of the [[Physical God]] who created the Transformers, and who seems to encourage them cooperating with other species, especially humans. Retroactive [[Fridge Brilliance]] perhaps?

** One of the very first things we see on the planet, in the pilot, is a huge ''fire''. Later episodes revealed that under the surface, there is organic earth to be found, and if we go all the way trough ''[[~~Beast Machines (Animation)|~~Beast Machines]]'', it is out-right stated that plant life did indeed live on the planet. The lack of visible atmosphere in the artwork seems to be the biggest problem, as everything else suggests there is one.

** One of the very first things we see on the planet, in the pilot, is a huge ''fire''. Later episodes revealed that under the surface, there is organic earth to be found, and if we go all the way trough ''[[Beast Machines]]'', it is out-right stated that plant life did indeed live on the planet. The lack of visible atmosphere in the artwork seems to be the biggest problem, as everything else suggests there is one.

* ''[[Invader Zim]]'' again. Irk, Foodcourtia, Earth, and Conventia don't all need to have the same pressure and those there need not all breathe oxygen as, at least in the case of the Irkens, they have atmospheric processing units (in the PAK). No matter what planets the Irken Invaders go to, they can always handle the atmosperic pressure. Of course, it may be possible that many of them are wearing their invisible space helmets, but that's kind of unlikely. Until, of course, it [[Weaksauce Weakness|rains]].

* ''[[Fairly Oddparents]]''. Cosmo doesn't quite understand what's wrong with visiting 'The Planet Of Not Enough Atmosphere'.