Orifice Evacuation

A variation of Body Horror, where a creature is inside someone else, and then leave through an established opening of the body (as in naturally, not a cut or piercing), even if it's not really an opening (like the navel). It could be the mouth, the nostrils, the ear, or through orifices below the belt. Pores could even count. The point is that the orifice is pretty much intact when the creature leaves.

Sometimes this can kill the "host", sometimes the host lives, or sometimes the host can already be dead.

Sometimes this can be horrific, but sometimes not. It depends on the nature of the evacuation. As the picture shows, it can even be Played for Laughs.

Compare Chest Burster (when the creature makes its own orifice to leave, or mutilates an orifice to get out), Giving Up the Ghost.

Contrast Orifice Invasion, Face Full of Alien Wingwong.

Examples of Orifice Evacuation include:

Anime & Manga

A small devil leaves through a guy's mouth in an episode of Yu Yu Hakusho. Strangely enough, The Abridged Series let that moment slide by without a comment.
In Naruto when the tailed beasts are shown being removed from their hosts they exit from their mouth and eyes.
- In the anime Itachi does this with a crow during a Mind Screw genjutsu.

Comics

The recent Titans Annual #1 has Kid Eternity being wrapped around a computer output input cable kind of combining this with naughty USB inputs, disabling his powers by going down his throat. Or summink.

Fairy Tales

A common fairy tale punishment for rudeness and deceit is to have the afflicted spew toads and reptiles from their mouth when they try to speak.
- It's often paired with a good person rewarded by having roses and diamonds come out. Although the reward seems like Blessed with Suck, since roses and diamonds seem like they would be even more painful in one's throat then something smooth like a snake.

Films

A cockroach leaves the mouth of Kim Jong Il after he is apparently killed at the end of Team America.
- Actually, the roach WAS Kim Jong Il.
And a whole roomful of roaches leave Mr. Pratt's mouth, wounds, and so on in Creepshow.
In Bruce Almighty, a gang pushed Bruce around, and he later got revenge by taking the leader's comment about monkeys flying out of his ass literally. And after Bruce sets the other members away, he "returns home"...
In the movie Evolution, Dr. Harry Block finds himself the unwilling home of a parasitic alien. It's not shown how it went in, but it was extracted through his ass. Not willingly, either.
In Tales from the Darkside: The Movie entry, the cat crawls inside someone's mouth. In the book, the cat burrows out of the stomach, but in the movie, he leaves the way he came in.
In Snakes on a Plane, a snake is shown slithering out of a victim's mouth just to drive home the fact that he's dead.
The Ceti eel crawling out of Chekov's ear in Star Trek II the Wrath of Khan, of course.
A spider crawls out from a corpse's nose in Arachnophobia.
In the second Poltergeist movie, the father swallows an evil-possessed worm from a bottle of tequila, then barfs it back up when it starts growing larger inside him.
A remarkably stupid version in the 1988 film The Uninvited: a mutant cat monster that hides inside a normal cat. It's about the size of a rat when it crawls out of the cat puppet, then grows to about the size of a puma.
In Resident Evil: Afterlife Albert Wesker is infested with... something that occasionally peeks out of his mouth. Much like the Plagas from the video games, it has four insectile pincers and would probably take your head off.

Literature

When Ron broke his wand in the second Harry Potter book, he tried to make Draco puke out slugs after he insulted Hermione, but it backfired on Ron.
- This scene was gruesomely recreated with loving detail in the second movie adapation.
- The Death Eaters' symbol, a snake emerging from the mouth of a skull, is a variant of this.
- Nagini and Bathilda Bagshot...
The Yeerks in Animorphs enter through the ear to take control of the host's brain, and leave the same way every three days to feed on Kandrona rays.
- Rachel's burping up of the crocodile in "The Reaction". We aren't told exactly what orifice it came from, but she's definitely intact once it leaves.
In one of Danish writer Jorn Riel's books, a parasitic worm leaves its host's body through his tear duct. It's not particularly painful or dangerous...at least for the host. Most of the damage is incurred by his mates, who argue about it so much the whole thing ends up in a fist fight.
Several of David Drake's stories feature Man-Eating Plants and/or When Trees Attack. At least once, a man died in his sleep while roots grew up into his body ... and then a leafy tendril extended out through one nostril.

Live Action TV

An episode of CSI had a rat leave a body through the mouth. Inspired a Quip to Black by Grissom.
- Another episode had a tapeworm crawl out of a corpse's mouth.
- Bones did the same thing with a crab, and averted it with a boa constrictor (which exited via a corpse's torn-open gut instead).
On Buffy the Vampire Slayer Willow's resurrection of Buffy is accompanied by her choking out a large snake, apparently as a trial by Osiris.
In Primeval, the parasites crawl out of the mouths of their victims' corpses.
In Fringe, a drink is spiked with a genetically altered cold virus that expands into a giant slug (about the size of a rabbit) within the victim's body before exiting via the throat, choking the victim in the process.
In the Merlin episode "The Witchfinder" one of the witnesses the Witchfinder drugs to make hallucinate claims to have seen a sorcerer cough up a toad. Later on, Merlin makes the Witchfinder cough up a toad.
In a real life incident recounted on Monsters Inside Me, a man who'd gone swimming in a pond in India started getting nosebleeds. Several days later, the leech that was causing them revealed its presence, extending its mouth out of the man's nostril.
A popular trick for witches in Supernatural. Always involving Squick - one witch killed a man by hexing him to cough up razorblades.
One of the escaped souls in Reaper could do this. While the soul could and did turn entirely into insects, one of the times was prefaced by the soul releasing a swarm of insects from a Skyward Scream.
One of The X-Files monsters of the week was a guy with... some sort of... spider creature... implanted inside by ex-Nazi scientists on orders of The Conspiracy. The creature leaned out of the mouth, did the killing, then hid back in.

Mythology and Religion

This goes all the way back to the Hittite myth called Kingship in Heaven. The god Kumarbi decided to overthrow the sky god Anu, wrestling him and biting off his genitals. This made Kumarbi pregnant with three deities: Teshub (the storm god), Tigris (the river), and Tasmisus. Since he had no actual birth canal, they had to emerge by other means. Teshub came out via "the good place" and we don't know where that is.

Tabletop Games

A 2E Dungeons & Dragons spell called Vipergout let its casters do this to themselves on purpose as a weapon.
- Retooled for Third Edition and presented in the Spell Compendium.

Video Games

The first Lego Island game. There's an ingame mission where you drive an ambulance around the island, making the occasional stop here and there. My memory is sketchy, but one of them is at the Pizzeria where you see a choking guy who after being helped by paramedics, barfs up a whole live Shark that's bigger than he is, and that shark then barfs up a live dog, and then the dog barfs up a live cat, and so on. It was some sequence like that.
Not really an exit, but a reveal: In Raidou Kuzunoha vs. the Soulless Army, the resident General Ripper is revealed to have been hijacked by a small god by forcing the man's mouth wide open, showing the grotesque little creature.
- The Hiruko are shell-like parasites that seem to enter (implied) and departs from their Victim's necks like the Gao'uld example above.
In a Tradewinds Caravans story, the eldest Jasaret daughter's "curse" is to have all manner of frogs, insects, and other small animals constantly flowing from her mouth when it is open. (At least one NPC notices her sneeze out a hawk.)
In the latest Aliens vs. Predator, Weyland-Yutani is farming aliens in human hosts, using canisters over the hosts' chests to capture the creatures as they emerge. One alien circumvents this trap by emerging through its host's mouth.
In Resident Evil 5 the Majini are all infested with variant Plagas parasites. Occasionally one of these will emerge from the victim's mouth as a much larger mouth with four pincers that will tear your head off if you let it.
- Sometimes the Plagas will also emerge from a victim's neck cavity once you've blown their head off. Arguably doesn't count, since the parasite basically acts as a replacement head.
- Ouroboros takes this trope Up to Eleven, emerging as a black slime creature from every pore of the victim's body. Then there's what it does to Excella, which you can watch here.

Web Comics

One of Wonderella's powers is to spew a large octopus out of her mouth. The alt text made it clear if this was Anime, the octopus would be forcing its way in.
In Gnoph, a Gnoph symbiote lives inside one of its host's lungs, and can enter and exit using the mouth. The host needs to take hormones to prevent the Gnoph from growing too large to fit comfortably, or else Body Horror ensues.

Real Life

Squicky in the extreme, but some internal parasites eventually leave the body this way, either as part of their life cycle or upon the death of their host.
In 1726, a woman named Mary Toft became (in)famous in England, as she'd reportedly begun giving birth to rabbits. Investigation revealed that she was "birthing" pieces of dead rabbits, which she eventually confessed her husband had purchased; she'd inserted them into her birth canal for later expulsion, in a weird attempt to gain fame and a possible pension from the king.
It's not unheard of for people with tapeworms to, ahem, expel, in whole or in part, their uninvited guest during a visit to the toilet.