No Conservation of Energy

""I consider the Laws of Thermodynamics a loose guideline at best!""

- Vaarsuvius, Order of the Stick: On the Origin of PCs

Most of us with a basic knowledge of physics know that Mass-Energy in equals Mass-Energy out. Whenever work is done on an object, energy has to come from somewhere. When you lift your fingers to type, energy from a chemical reaction is used to do it. Which raises the question, when a wizard does it, where does that energy come from?

In Speculative Fiction, the Law of Conservation of Energy is disregarded more often than it is honored. Whether it's magic or psychic powers, people can perform superhuman feats while the question of where the energy comes from to do them is never answered. Things can be set on fire, lifted with the power of the mind, crushed, or altered without an apparent energy source.

Sometimes it is explained by having a character get all that energy from being a Big Eater and/or Heavy Sleeper. Which in itself can be an example of Artistic License: Biology.

This can also work in reverse with energy apparently being destroyed. Actions that should create a huge amount of energy, particularly energy in the form of heat, don't.

The Law of Conservation of Mass is similarly ignored, particularly when involving powers that create something from apparently nothing or where shapeshifting is involved.

This can lead to weird results when you start Abusing the Kardashev Scale For Fun and Profit.

It is generally more acceptable in Fantasy settings, especially with Art Major Physics, although more thorough authors will try to explain where the power for magic comes from. Some author try to maintain conservation by invoking a law of Equivalent Exchange, with varying degrees of success depending on how well it's thought out.

Of course, it could be argued that any use of energy which is unequivocally already supernatural to begin with, just by definition doesn't necessarily have to follow physical laws anyway.

Perpetual Motion Machine is a subtrope of this. See also Shapeshifter Baggage, Elemental Baggage, Art Major Physics. This trope is often implied among certain Required Secondary Powers.

Anime and Manga

 * Dragonball Z: These people can destroy PLANETS. They can casually shoot beams from their hands that level mountains. Aside from a somewhat large appetite, this is never explained.
 * In Gurren Lagann, it's a key plot point that Spiral Power does not conserve matter or energy.
 * Averted hard in Fullmetal Alchemist, where that extra bit of energy needed to break the laws of physics is always fully explained; In the Anime, the power comes from Alchemists follow the rules normally, but they can start Abusing the Kardashev Scale For Fun and Profit if they
 * In the manga and second anime, this becomes 'geothermals' and 'tectonic activity' (it hadn't yet been explained in the manga when the first anime was made). For a bit it looked like Father was going to have done something really devilish when he gave proto-Amestris the energy-capture equations, but it looks like it really was tectonics and Mei was just sensing Father.
 * In Zettai Karen Children, the Psychic Powers are explicitly stated to violate the conservation of energy and not bound by normal physics therefore allow the protagonists to Screw Destiny.
 * One Piece has examples of disregarding this law (Zoan-type and Logia-type Devil's Fruit Users) and flimsy explanations (Big Eaters to gain all the energy they need).
 * And also in the One Piece world exist some magical shells called Dials, one of them, the Reject Dial not only has the property of absorbing kinetic energy and then release it, but also release ten times the kinetic energy that was absorbed.
 * A Certain Magical Index: Touma's fist doesn't just nullify magic and esper powers. No, it also nullifies inertia. That's why he can effortlessly block the punch from a golem made of solid rock that stands a good thirty feet tall. Then again, given that something thirty feet tall and made of solid rock shouldn't be able to move under its own power in the first place, it could be argued that he's actually enforcing the laws of physics by getting rid of kinetic energy that should never have existed in the first place.
 * Code Geass has their own version of a nuke known as freia (or "freya" depending on the translation). Instead of releasing a fast amount of energy, the freia creates an expanding energy field, which after a few seconds implodes and leaves only a void. It has never been explained what happened to all the matter that suddenly disappeared into thin air.
 * Ranma ½, being a Supernatural Martial Arts Shonen series, is naturally rife with this, but a very special mention goes to the final enemy in the series, The Phoenix King Saffron:
 * He can throw blasts of flame so powerful they not only singe rock, they cause superheated air to rush outwards with enough force to punch down walls of said rock in an instant. One sweep of his wings created a pillar of flame powerful enough to destroy the entire top half of a hollowed-out mountain. Try to collapse a cave using a flamethrower, we'll wait.
 * He can regenerate any injury, no matter how serious, due to being a phoenix that creates its own flame. Where the mass comes from, or how he creates that regenerating flame in the first place, is a mystery.
 * His mere Battle Aura is hot enough to melt rock into lava and form a Sphere of Power of blinding white light around him.
 * He can release heat beams several dozen meters wide strong enough to vaporize entire rows of mountains. Vaporize. And do this with zero preparation (except to strike a pose and call out the attack.) And then do it AGAIN immediately afterwards, pausing only to realize the first blast didn't take, with no recovery time.
 * And last but not least: the incarnation of Saffron that Ranma et al encountered in the series is merely an immature brat who was in a very bad mood. The immortal Phoenix King's true role is to simply sit tight on his perch and provide endless ambient heat and light for all his subjects so they're comfortable. He's not even once shown to have a big appetite or something. He just generates infinite amounts of heat because he does.
 * In Puella Magi Madoka Magica, the Weasel Mascot specifically mentions that magic defies the laws of thermodynamics.

Comic Books

 * This is so standard for super powers it almost goes unnoticed. Nearly every Superhero and Super Villain with powers produces far more energy than their body contains. Occasionally you'll see a Hand Wave like Cyclops' or Superman's "powered by sunlight" or Havok of the X-Men's "powered by cosmic rays", although if you do the math on their demonstrated energy usage, it doesn't really add up. It also means that with so much potential energy stored in their bodies, every time they get their powers neutralized, they should explode like atomic bombs.
 * In Ultimate Fantastic Four, Ellis tries to avoid this; he still has Reed "eating" air. Invisible Woman's explanation consists of a Lampshade Hanging, and Ben's power goes unmentioned. The Human Torch's bio-fusion is highly implausible but at least gives a Hollywood Science Hand Wave to his energy source. Every other book in Ultimate Marvel, well, decidedly less so.
 * Several novels and Alternate Continuity series (and occasional Canon theories) have proposed that many or most supers draw energy from Another Dimension. As with most canon elements these days, whether or not this is given any weight varies Depending on the Writer.
 * Some fans have theorized that Superman's gut is actually a thermonuclear reactor, or even a matter-to-energy converter, that squeezes every last megaton of available energy out of the food he eats. (This would explain why he never goes to the bathroom...)
 * Several mass-changing characters actually need to absorb mass from outside themselves; Stronghold of Valiant Comics, a Static Shock villain, etc. Most just "get heavier".
 * Of the Justice League's "Big Seven", only Superman and Martian Manhunter still run afoul of this trope. Wonder Woman, The Flash, and Green Lantern are all explicitly powered by Phlebotinum or magic. Aquaman is pushing it with his ability to swim at 100 miles per hour.
 * Done in Steelgrip Starkey And The All-Purpose Power Tool. The tool is driven by "technalchemy", which allows it to run with no visible power source, synthesize new components and materials out of thin air, and is apparently indestructible.
 * Averted in Rising Stars.

Fan Works

 * Magic and psionics in With Strings Attached are said to be powered by the universe's Field of magic, which the user taps into and shapes. Although one unversed in magic will not feel the Field around them, Paul discovers after he learns to cast spells that he is now aware of the ebb and flow of raw magic around him.
 * Jeft implies that magic and energy are related when he mentions that to keep Paul's strength from overwhelming him, much of it is transformed into raw magic and returned to the Field before it leaves his skin.

Film

 * In the remake of The Day the Earth Stood Still, the heat energy from the spacecraft rapidly decelerating should have turned the UN and the surrounding landscape to molten slag.
 * Between the mothership, the ship reactors, and...well, everything... don't think about where all the energy comes from or goes in Independence Day.
 * Parodied in Galaxy Quest, when the crew has to land on a hostile planet to retrieve a "Beryllium Sphere", because it supposedly powers the ship, for reasons completely unexplained and unknown, except that it happened on the TV show.
 * This is a direct parody of the Dilithium Crystal that somehow makes warp drive possible in Star Trek. It is there to "mediate" the matter-Antimatter reaction and create a pair of tuned plasma streamers. This is only explained that way in official material outside of the show, which makes this All There in the Manual.
 * In the 2009 Star Trek movie, Spock uses a drop of "red matter" to collapse a supernova into a Negative Space Wedgie via some sort of chemical reaction. The wedgie seems to work like a Hollywood black hole, sucking up the entire supernova—and Spock's ship—with a lot of mass that appeared out of nowhere. Even if this isn't technically how it works, there's no obvious way to explain how a tiny blob of goo reversed the momentum of an exploding star. These little goo-blobs are also capable of making entire planets collapse in on themselves into Wedgies which seem to have much more mass than the planet did. And it's not just that the blobs are extremely dense; Spock has about a million times the supernova-erasing dose in his ship, and he can easily carry a canister of the stuff by hand.
 * In Honey I Shrunk the Kids, the principle behind the shrink ray is explained thus: atoms and molecules are made up largely of empty space between the subatomic particles. The ray shrinks an object by reducing this empty space. However, this should mean that a shrunk object retains its mass. Ergo, the shrunk children should be just as heavy and just as strong as they were at full-size. There should be no plot, because there's no way they could get swept up in the garbage by accident, and they should have the strength to jump up and activate the machine themselves - assuming their incredible density didn't make them fall straight through the floor.

Literature
"Ponder: Er- It's not as simple as that. Ridcully: Why not? Bring him back by magic. We sent him there, we can bring him back. Ponder: Er... it'd take months to set it up properly, if you want to get him back right here. If we get it wrong he'll end up arriving in a circle fifty feet wide. Ridcully: That's not a problem is it? If we keep out he can land anywhere. Ponder: I don't think you understand, sir. The signal to noise ratio of any thaumic transfer over an uncertain distance, coupled with the Disc's own spin, will almost certainly result in a practical averaging of the arriving subject over an area of a couple of thousand square feet at least, sir. Ridcully: Say again. Ponder: I mean he'll end up arriving as a circle. Fifty feet wide."
 * In the Harry Potter universe, the answer to the riddle about where Vanished objects go is that they merge with the rest of the universe. This implies that they don't create matter when they Conjure items, either. Wizards just steal matter from their surroundings, reorganize it into the shape they want, then return it when they are done.
 * Played straight with broomsticks, however. They fly as high as you like, but they never seem to need fuel, except maybe the wizard's magic?
 * Since the wizarding community doesn't believe anybody can reach the moon (not only did they not do it first, they think space travel is impossible), and they've got spells to handle the environmental problems, there probably is a limiting factor. Or some ambient planetary field all magic is powered off of.
 * Also played straight with Freezing Charms.
 * Averted in Anne McCaffrey's Talent series, which explains that the power necessary for the telekinetics to hurl spaceships around like toys comes from massive generators. Psychic activity (with or without a generator gestalt) also burns a lot of calories, meaning that, while a telekinetic with no generator handy can get the job done quicker, he's still doing the same amount of work as someone doing it by hand. Many of the telekinetics are shown eating some pretty high-calorie meals and snacks throughout the day to keep their strength up, and get extremely fatigued after teleporting very large objects (even with the generators helping).
 * Also, it's stated that energy must be absorbed when negative work is done (for instance, teleporting an object from orbit down to ground level), although simply being the conduit for such large amounts of energy can still place enormous stress on physical systems.
 * Also averted in The Ship Who... Won. A brainship finds a world where magic actually works, complete with all the standard No Conservation of Energy tropes. Then they discover that.
 * Averted in Robert Asprin's Myth Adventures book series: magic is fueled by ley lines crisscrossing the worlds, and you have to be tapped into those forces to be an effectively powerful wizard.
 * It's often hard to reconcile stories that involve Shapeshifting with the related law of conservation of mass. In one of his Fafhrd and The Gray Mouser books Fritz Leiber makes an exception by having a character who's shrunk needing to find a few zillion spare atoms if he wants to get back to normal size.
 * Isaac Asimov's The Gods Themselves. The trope is subverted because the law of conservation of energy is upheld when a device which appears to obtain energy out of nothing actually gains it by taking advantage in the differences in physical laws between two universes (at the loss of 20 electrons in our universe and the gain of 20 electrons in the other universe, as well as positron radiation).
 * And the obvious thermodynamic implications apply --
 * Subverted in Larry Niven's The Magic Goes Away fiction. All magic is fueled by mana, a natural non-renewable resource. The setting is a 'lost age' of high magic on the decline, as the last of the world's magic is expended, leaving behind the mundane world we live in.
 * Hand waved in David Eddings's 'The Belgariad' series. Belgarath explains that nothing can truly be destroyed (it just changes energy forms), and trying to 'unmake' something will end up with some unfortunate consequences.
 * Also played totally straight in that they seem to be able to create whatever they want, with no requirement to take energy/mass from anywhere for it.
 * In the books, it is explained that creating things works off your own creative energies, which is why it's much more exhausting to make a door than to blow it to pieces. Also, the inability to destroy things doesn't come from the conservation of energy, but from the universe itself - which is, apparently, alive and says "No you don't!" to attempts at unmaking, something it doesn't even allow the gods to do. Long story short: It's magic, it plain doesn't work by the laws of physics (and the books certainly don't try to pretend that it does).
 * On the other hand, it does. Turning a stone around takes less effort and energy if you simply get it rolling by pushing at the top than it does if you lift it up, turn it around and then drop it upside down, which leaves you both incredibly tired and pushed down into the ground by the opposite reaction of it's weight if you don't brace yourself. Moving air gradually takes less energy than moving it all into a storm-strong wind in an instant and even then it's taxing enough to leave the very experienced person who does it passed out from exhaustion. Creating something new usually involves taking something that's similar in some way (like the type of matter or the right shape) and changing that (and still takes a great deal of effort) and unless you've got about several thousand years of practice or a handy near inexhaustible supply of power in the form of an orb most things are very taxing. Though the Malloreon tends more towards this trope.
 * The Animorphs books address this - when they shrink down to cockroach size, their extra mass is shifted into Z-Space, the same dimension that FTL starships travel in. Likewise, when they morph something larger than themselves, the extra mass comes from the same place.
 * What merits complaining about there is stuff like 'How are portals into Z-space opened,' 'Where does that energy come from,' etc.
 * Terry Pratchett's Discworld novels try to at least give this a nod. Teleportation's pretty risky too, especially with the knowledge that even if you're sitting on a chair you're still really moving somehow.


 * Salacia, a vampire in Thud, has issues with this when she turns into a bat. She has to settle for turning into many bats. Which are a pain to get back together...
 * Discworld magic also obeys the conservation of momentum (except for flying broomsticks). If a wizard wants to hurl himself from the ground to the top of a tower, he has to cause a stone with an identical weight to his to fall from the top of the tower and magically link his ascent to the stone's descent.
 * Magic carpets are also exempt, although this may be because they use magic in a different way (in 'Weird Sisters' Magrat's broomstick is shown to lose its capacity to fly if it loses too much magic, and in Equal Rites, Granny's broomstick doesn't work in sunlight, although this is later solved).
 * Telekinesis also gets a brief mention when it is pointed out that when you try and lever an object using your own mind as a fulcrum, the most likely outcome is that your brain gets forced out of your ears. Much training in the psychic equivalent of a gym is required.
 * While the Discworld novels are reasonably respectful of conservation of energy (as much as one can be while satisfying the demands of Narrative Causality and Rule of Funny) they often play fast and loose with entropy. A lot of Tiffany Aching's practical magic, in particular, involves moving heat from one place to another.
 * Wild Cards shapeshifters often have a Hand Wave of "virtual particles", basically acting in ways that in no way resemble the virtual particles of real-world physics.
 * However, when "Captain Trips" undergoes an uncontrolled transformation into the gigantic creature called "Monster" in one book, the narration makes it very clear that the process is sucking up a huge amount of the nearby landscape to provide the mass for the creature's huge body.
 * Alastair Reynolds Revelation Space novels feature two examples - the Conjoiner engines, space drives with a more-or-less unlimited energy source used by lighthuggers to get around, and Cryo-Arithmetic computers used to siphon heat out of the universe. The former is subverted in Redemption Ark when it is revealed that
 * In The Dragon and The George, the trope is either slightly inverted or subverted. Speaking on the subject of the power available to mages, the wizard Carolinus irritatedly says (paraphrased), "Just because a number's infinite doesn't mean you can use it to get something for nothing." (This may be true in this universe, as he's apparently referring to Cantor's hierarchy of infinities, and spells may require infinite expenditures.) As with the Young Wizards series above, later books note in the background the development of ways to tap new sources of power, some of which probably provide infinite energy, but which still avert the trope.
 * Dan Brown's Angels & Demons is based around the female protagonist/her dead father pumping vast quantities of energy into the LHC to form Antimatter, which they can then annihilate with normal matter to provide 'clean, sustainable energy for all' (instead of the bomb it inevitably becomes). It somehow never occurs to either of these highly trained scientists that they would have to put more in energy to create the antimatter than they could ever get out. The second law of thermodynamics wins again.
 * Antimatter is pretty much impossible to contain in real life. You'd be hard pressed to find a less portable energy source.
 * Lampshaded in Firestarter. After a government experiment in which Charlie McGee vaporizes a cinderblock wall with her pyrokinetic powers, the next chapter is an Interdepartmental Memo in which one of the evil government scientists points out to the head evil government scientist that, despite producing 30,000 degrees of spot heat, the nine-year-old girl in question burned about as many calories as if she were reading a good book—leading the seriously weirded-out scientist to wonder just where the hell the energy is coming from (and to start thinking about stuff like black holes and things we breathe a sigh of relief that we can only observe from millions of light-years away and pretty much wondering if this little girl is some kind of rift in the very fabric of the Universe). The last lines of one of penultimate chapters suggest that she might be tapping into the Sun for her power, and that she might one day be able do more than just draw on it.
 * Alan Dean Foster's Humanx Commonwealth series has a brain-bending use of this trope in its mechanism for FTL Travel, which involves generating a small black hole in front of your ship and letting it "pull" you along until it evaporates, at which point you generate a new black hole, and so on. The first novel in which it's introduced even lampshades it by having the viewpoint character struggle with the concept.
 * Moorcock's series The Dancers At The End Of Time averts it: one million years in the future the advanced technology of mankind has turned the remaining members of our species into undying Reality Warping Physical Gods. Except that this technology cost so much energy that the Degenerate Era (an era that should comes by 100 trillion years from now) has already began: in other words, by achieving godhood, mankind has divided by one hundred million the lifetime of the universe.
 * Averted in regards to conservation of mass in the Deverry novels. The mazrakir (shapeshifters) all change into an animal form the same size as their normal form. Nevyn pokes fun at the old 'sorcerers turning people into frogs' story by pointing out the stories never mention that the frogs would have to be big enough to ride.
 * Averted in Eric Nylund's A Signal Shattered where an alien merchant sells the people of Earth a teleportation device which works by borrowing a negligible amount of the Earth's rotation. Needless to say, widespread use of this "free" technology results in Earth's destruction.
 * Starships in the Honor Harrington universe use the Impeller Drive, which create gravity waves that the ship can "surf" on at over 500 G's acceleration. A starship requires far less energy from its fusion reactors to run its Impellers than the amount of kinetic energy it gains from that acceleration.
 * In The Dresden Files, magic "still has to do business with physics" so that energy can't come from nowwhere. Generally energy is drawn from latent magical energy in the world, which is produced by life and emotions, though there are plenty of other sources, such as large leylines of raw energy (which should not be messed with unless one is a skilled wizard), Hellfire (from down below), Soulfire (drawn from one's soul) or even from existing energy, like latent heat. The latter has been used multiple times by Harry Dresden to freeze things by ripping latent heat from his surroundings, like pulling the heat from a lake's water to freeze it, or pulling the heat from around a vampire to freeze it (and then throw that heat at another vampire to burn it to ashes).
 * The titular character of The Chronicles of Professor Jack Baling wonders about this one, both as it applies to the perpetual motion machine created by his student and his own disintegrator ray. Using the latter in quick succession does end up blowing a fuse, but the amount of energy involved in powering the thing in the first place is staggering. He shouldn’t be able to get that much juice at once in the first place.
 * The titular character of The Chronicles of Professor Jack Baling wonders about this one, both as it applies to the perpetual motion machine created by his student and his own disintegrator ray. Using the latter in quick succession does end up blowing a fuse, but the amount of energy involved in powering the thing in the first place is staggering. He shouldn’t be able to get that much juice at once in the first place.

Live-Action TV

 * In Star Trek, while not involving Functional Magic or Psychic Powers in this case, whenever phasers vaporize people, rather than create explosions from that much matter losing cohesion, they just disappear. The in-canon explanation is that they don't vaporize, phasers convert matter into undiscovered particles that dissipate into Subspace or Hyperspace.
 * And there are the various shape shifting aliens that can go from something the size of a mouse, to a human and back. While this could be explained as simply increasing density rather than reducing mass, Dr. Bashir even notes Odo's ability to change mass in one episode of Deep Space Nine (without even giving a theory as to how). Odo at one point had to reinforce his floor because some of his forms were too heavy for it to support.
 * Hand waved at one point; Changelings like Odo are a kind of partial Energy Being whose form overlaps with normal space and subspace, allowing them to draw their mass into or out of normal space. They can also become FIRE and other energy forms with practice.
 * Hand waved at once on Buffy the Vampire Slayer. Most of the time, magic works like this. But once, Willow said something about rearranging elemental forces. Making a fire caused a rainstorm.
 * Zatguns on Stargate SG-1 had similar issues to Star Trek phasers, until writers decided that was stupid and stopped using that feature.
 * Another prime offender in Stargate is Naquadah and it's various sub-forms which can somehow turn a normal nuclear bomb into a continent buster among other insanity. Calculations by fans indicate it must have an energy density greater then antimatter, which is not physically possible.
 * Averted by ZPM's in SG-1 and Atlantis, as they draw energy from subspace, and so don't need to follow the conservation of energy law. And yet, this is the one form of Applied Phlebotinum on the show for which running out of energy (after performing some truly amazing feat) is often portrayed as an issue.
 * In Space: 1999 during its second season one of the main characters (Maya) constantly changed shape, size and mass without even a nod given to where the energy/mass had to come from/go to for this to work.
 * Almost averted in Eureka when a decelerating spacecraft needed a high-energy "cushion" to slow it down. While the energy from the spacecraft was absorbed by the field, there's no mention of what the field did with the energy.

Tabletop RPG

 * Dungeons & Dragons. In the AD&D 1E Dungeon Master's Guide, Gary Gygax explained that the power of wizardly magic came from other dimensions, and the power of divine magic came from deities.
 * In 3.5 it's explicitly stated that while you do need to follow conservation of energy, you can pull any extra heat you need, for example, from the elemental plane of fire. Which is infinitely large and all of it is fire. So the only real limits are how skilled you are at moving things around. Once you get into the plane of shadow, or the positive and negative energy planes, it gets weirder.
 * Explicitly averted in GURPS's default magic systems as of 4e. Mages use ambient mana to power spells (if there's not much mana they can seriously hurt themselves). Clerics channel power directly from a deity. Ironically psi powers, which are treated as more scientific, give no explanation for how they operate without outside energy.
 * One of the example technologies available for T+ 4 ships in Diaspora is the ability to dump heat into another dimension. This is important, as the game remembers that hard vacuum is an insulator.
 * Averted in both Warhammer 40,000 and Warhammer Fantasy. In the former psykers are able to open up miniature gateways to the chaotic realm of the Warp with attached risks of drawing daemons through with the power they use, in the latter wizards are able to draw upon the ambient Winds of Magic (which have chaotic and irregular power levels, no less) to fling spells.

Video Games

 * Semi-averted in In Famous. Cole's special powers use up stored electricity, which can only be recharged by absorbing more from some electrical source. On the other hand, his basic lightning attack doesn't use up any stored electricity. Also, the amount of electricity gained can be a little strange. For instance, you gain a surprisingly large amount of electricity by draining a person.
 * Made worse when you consider that his basic lightening attack can be used so that it actually "generates" electricity! Though you do actually have to hit something that would give electricity if drained, so it may just be transferring that to you. It still begs the question of why Cole can't just use the energy to recharge his power meter.
 * This is actually a plot point:.
 * After being seriously harmed at the start of the second game, many of his powers are lost or altered. The most noticeable effect is that Cole's basic lightning bolt required electricity to use at all times, drawing from the same energy pool as his other powers.
 * Averted in Geneforge. To make creations, you have to keep up your essence, and to get essence, you have to drink from essence pools, which are filled by whoever is tasked with making essence in a long, highly dangerous process.
 * Pokémon is a pretty big offender, with Elemental Baggage and Poke Balls changing in size between, roughly, a golf ball to a softball.
 * Also evolution. At level 20, Magikarp, weighing a measly 22 pounds, suddenly explodes into Gyarados, who weighs 518.1 pounds. Where does all of that extra mass come from?
 * All the details of Pokemon biology that come with each Pokedex entry might as well just not exist. Anyone with half a brain should know that Pokemon shouldn't continuously exhale water as if they're attached to a hose or a pipeline. How does Squirtle store all that water into its tiny body? Flapping your wings can realistically create a gust of wind, but it would also send the offender flying backwards.
 * Considering that the Pokemon universe (and, presumably, laws of physics) was created by a Pokemon, this might be a case of Screw the Rules, I Make Them
 * In EVE Online, the energy conservation rule doesn't exist at all. The main example would be the logistics ships, that can use (since they have energy usage bonuses on certain modules) a module giving 324 GJ to an ally for the cost of only 108 GJ energy usage. There are probably more examples.
 * It gets even worse with the above example. Two logistics ships can transfer 324 GJ of energy every few seconds to each other while only using 108 GJ each to do it. This results in each ship gaining 216 GJ of energy every 5 seconds that literally comes from nowhere.
 * Another example would be the "Thermodynamics" skill description: "Also gives you the ability to frown in annoyance whenever you hear someone mention a perpetual motion unit."
 * The Portal games play merry hob with physics. Consider the things you could accomplish with a zero-energy link between two discrete surfaces in spacetime—setting up a perpetual motion generator would be trivial, not to mention violating relativistic causality at a whim. Portal 2 introduces materials that are just as bizarre, including gels that have greater than 100% elasticity and a negative coefficient of friction, all gleefully Hand Waved by Aperture Laboratories' reckless approach to research.
 * Averted in Dragon Age, mages are lucid dreamers with the ability to draw some element of the Fade into the real world to make it respond to their will. And in most cases they still have to use lyrium as a power source.
 * In Dwarf Fortress smelting, forging metal items, and other things that require great heat can get the heat from magma rather than by burning fuel. But since in the game magma remains at the same fixed temperature regardless of how much heat has been extracted from it, a small bit of magma isolated from the planet's core can supply an endless amount of heat energy.
 * There is also the Dwarven Water Reactor, which is a power-producing perpetual motion machine that relies on using a pump to raise water to power multiple waterwheels (which are hooked up to the pump and whatever else needs power)
 * Creatures with a fixed body heat (like magma men and fire men) are endless wells or sinks of heat coming from and going to nowhere.
 * Wooden items, if set on fire, will keep on burning until they are completely incinerated. Artifacts cannot be destroyed. The logical conclusion is to create eternally flaming artifact wooden weapons or coal statues.
 * Surprisingly, Super Mario Bros. somewhat averts this. Some of the characters are described as drawing power from stars inside them, which would provide more than enough energy for the things they do. There's still no explanation for how this works; and it's still played straight otherwise.

Web Comics

 * Averted precisely once in The Adventures of Dr. McNinja, here.
 * El Goonish Shive initially averted this with Grace, your average teenage everyday shapeshifter, who initially had a constant mass (and presumably variable density), no matter what form (even squirrel?). Then, once the TF gun is used on her, she's surprised to discover that her mass now does change with her form. This is apparently possible because both the TF gun and her shapeshifting powers use a type of energy that can be classified as magic. In addition, the magic users burn up Ki energy, which they constantly recharge, and can burn caloric energy instead, or use the Ki energy as a boost for things that normally use caloric energy. Still a little odd, especially considering where the Ki energy comes from, how immortals fit in, etc., but explained well enough for this trope to be largely averted—especially for comics, who get a free pass for some things like this.
 * How can anybody ignore Order of the Stick, the comic the quote above comes from? Definitely ignorable, as magic is a big part of the comic, but it is still Lampshaded, as are other laws of physics.
 * The Inexplicable Adventures of Bob acknowledges this, even if it is handled in a very toony fashion. Snookums started as a giant Kaiju and got compressed to the size of a basketball; he's shown to still be enormously heavy, but still not nearly as heavy as his original size would indicate.

Web Original

 * The Whateley Universe makes a few attempts to Hand Wave this, comic book style. For example, magic users need a suitable power source (Fey draws upon ley lines for this purpose and has trouble when those get disrupted badly enough) or else have to cast their spells from their limited personal supply of 'essence'. Energizers tend to be big eaters, although it's implied that the real source of their power may be outside themselves—Earth's magnetic field has been brought up at least once. Tennyo's body apparently produces antimatter naturally (inasmuch as the term applies to what seems to have involved into some form of highly advanced android body by now), which sort of explains where she gets the power for her destructive blasts and energy sword from. As with most comic book examples, though, it's still best not to poke too hard at the finer points of the 'science' behind it all.

Western Animation

 * In  Avatar: The Last Airbender , benders can create or manipulate their given element. This is hand waved as chi manipulation, but benders don't seem to be using nearly enough energy to do what they do, even assuming the human body contained enough energy for some of the Avatar-level bending, though it's never really stated how much energy the chi itself actually contains. This is especially obvious with waterbenders, who can change the state of large amounts of water from solid to liquid to gas and back again.
 * Specifically, the only benders who can outright create their element in the show are Firebenders, who ignite the air around them. The upcoming film alters this, requiring Firebenders to carry little lanterns around with them, much to their chagrin.
 * Lots of theories abound about where all of Generation 1 Megatron's mass wanders off to when he transforms in ..well, Transformers.
 * Not to mention Soundwave, Blaster, Optimus Prime's trailer... and then there's this...
 * Small aversion in Gargoyles. Word of God states the Gargoyles strength is fueled by solar energy absorbed by their bodies while they sleep during the day. However, Gargoyles DOES avert this trope nicely with its mention of how magic works, that energy is energy, etc...
 * In Futurama, Professor Farnsworth describes his ship's engines as having 200% efficiency and they used not to move the ship, but to move the entire universe around the ship. Another character comments that this is "especially impossible."
 * Made doubly hilarious by the fact that the writing team have a few physics degrees among them.
 * In Justice League Batman invokes the law of conservation of energy (well, he exchanges 'energy' with 'mass', but otherwise...) as an indication that didn't work the way its creator intended—there were no scorch marks, leftover atoms or increased ambient energy on the site, which it should have been had it worked as intended.
 * Batman the Brave And The Bold, of course, usually plays this dead straight. Still, there was a notable aversion in "OMAC Attacks!": Batman wonders how the villain keeps regrowing his weapons without losing mass elsewhere; it turns out he was absorbing the kinetic force of the Dumb Muscle's attacks against him.
 * An attempted aversion, anyway, since the Dumb Muscle would have to convert his own mass into energy to hit with that kind of force. Otherwise he's literally punching energy out of nothing, which is, admittedly, pretty badass.
 * Not to mention the amount of energy that is. In order to regrow a gram of mass, he'd have to punch with an amount of energy comparable to a nuclear bomb. If he was punching anything that wasn't hyper-efficiently absorbing it, the energy would most likely be released with pretty much the same effect.
 * He's also violating a few conservation laws by creating matter without creating antimatter. Admittedly, he could make the electrons by making an equal number of anti-neutrinos, which would largely go unnoticed, and baryon (proton and neutron) conservation is most likely more of a guideline. I think there might be one or two more he can't get around, though.