Kinkaku and Ginkaku were swallowed whole by the 9-Tailed Fox and start eating it from the inside, giving them some of its power.
This happens to Naruto again when Son Goku the 4-Tailed Ape catches him in his mouth. As before, Naruto escapes by creating so many clones the beast's is forced open.
In the One Piece Skypeia arc, Luffy and some of his companions are swallowed whole by a giant snake. Once Luffy realizes he's in the snake, he figures the quickest way out is to head for the tail. His companions talk him out of this.
This seems to come up rather frequently in One Piece, probably because it's a world stuffed to the brim with enormous sea monsters. This includes a man who literally has a vacation home inside a massive whale's stomach and the threat of being eaten by a goldfish that literally eats islands. And if you want to avoid this trope, don't go anywhere near the Calm Belts.
In chapter 5 of Tokimeki Tonight, Ranze mistakenly shapeshifted herself into a bread during a race and end up swallowed by her rival, Yoko. She managed to morph back and escape in the following chapter through Yoko's mouth when she was unconscious.
Blood-C boasts a rare example in which a character is eaten whole by a ball of hair, leaving only an enigmatic puddle of blood behind. Some other episodes feature people being eaten whole, but it is much more common for them to become horribly mutilated before actually being eaten.
For a more traditional example; in the final episode, Saya purposefully enters the body of an Elder Bairn through it's mouth to save Kanako and to kill it from the inside.
In Catnapped!, the rampaging monster Papadoll swallows dozens of citizens whole. It turns out he was just carrying them to his mistress to be used in her evil plot, because when he gets back to her, he spits them all out alive and unharmed. Curiously, the heroes who witness the "swallowing" seem to understand that the victims have been taken away and can be rescued, rather than assuming (as the audience might) that they were eaten.
A variant in Dragon Ball Z; Buu can absorb other fighters to gain their power (gaining the outfit of the strongest person he has absorbed in the process) by engulfing them in the pink goo he's made of, doing so to Gotenks (the fusion of Goten and Trunks, who defuses while absorbed), Piccolo, and Gohan. When Vegetto, the fusion of Goku and Vegeta, is absorbed (as part of his plan to free the others), he puts up a shield, which prevents him from becoming a part of Buu, but defuses back into Goku and Vegeta, who then journey through Buu's body to free the others.
In episode 5 of Attack on Titan, Eren gets swallowed whole by a Titan in his attempt to save his best friend. In episode 8, he then emerges unscathed on a different Titan. It gets explained on the next episode how that happened.
In an issue of Booster Gold, a transformed-to-rodent Blue Beetle is swallowed by an antagonist called Estrogina. After failing to free him, Booster despairs, until the spell changing Blue Beetle into a chipmunk wears off...
Most of the monsters in Felarya swallow their prey whole, but they do have stomach acid, and it's rare for the prey to get out alive.
The origin of Ultra Boy from the Legion of Super-Heroes has him being swallowed up by a giant space-living energy creature and being bombarded by its radiation before another ship blasted the side of the creature, letting Ultra Boy loose but giving him superpowers. (Because the Silver Age of comics is sometimes not very subtle, Ultra Boy's real name is Jo Nah.)
Played for horror in issue #33 of Grimm Fairy Tales, which adapts the obscure fairytale "The Three Snake Leaves". A scientist uses a snake-based elixir to cure his wife's fatal cancer, after being given a copy of a book containing this fairytale. Unfortunately for him, the book-giver is Belinda, the evil "Storyteller", and his wife, like the wife in the story, is overwhelmed by the instincts of the snake. Worse, just after reading this part of the story, he gets a call from the man who sold him the snake, explaining that he was given a snake-eating, offspring-cannibalizing king snake, rather than the intended coral snake. There is a Hope Spot when he sees his eldest son is alright once he rushes home... but the last panel shows he was too late to save his youngest son.
In Wormy, Bender the salamander was swallowed alive by a long-jawed mudsucker, only to cut his way out with a knife it'd also swallowed.
"Little Red Riding Hood", in the younger versions at least — there are a couple older variants where the wolf carves up grandma and lil' Red (and they, hardly surprising, don't get out alive).
"The Wolf and the Seven Young Kids": The wolf devoures all of Mother Goat's children, but they are rescued in the same way Little Red Riding Hood and her Grandma are saved.
"The Dragon Sliced In Two": In this Swiss fairy tale, a clever young shepherd named Juri tricks a brutish but gullible giant into believing that he is as strong as him, and to help kill a ferocious dragon to stop it from eating a princess. Unfortunately, Juri gets swallowed alive by the dragon, but as he tries to hack his way out of its belly with a knife, the giant kills it with a blow on its spine that causes it to split in two, freeing the hero, who through some more fast talking cons the giant into thinking they killed it together, him outside, the hero inside!
Films — Animated
In Pinocchio, Gepetto, Figaro, and Cleo get swallowed whole by Monstro the Whale, and Pinocchio later does as well when trying to find them.
Finding Nemo. Right before finally arriving at Sydney, Australia, both Dory and Marlin are actually swallowed up by a blue whale. And then, upon reaching Sydney, are swallowed by a pelican (which they escape from by choking him) and then are carried about in the mouth of another (friendlier) pelican.
At the end of Astérix Conquers America Lucullus gets eaten off-screen by Caesar's pet panther.
In An American Tail, Fievel is almost eaten by a cat but manages to climb back up it's throat and grab its uvula, causing a gag reflex that makes it cough Fievel up.
In An American Tail Feivel Goes West, Five ends up in Tiger's mouth by accident. He's fine when Tiger hears him.
In Hercules the Hydra swallows Herc whole, who decapitates it from the inside.
In How to Train Your Dragon, the Red Death swallows a Gronkle whole for not bringing enough food to feed it. Also, when Hiccup, Astrid, and Toothless try to flee from it, it is also seen devouring a Hideous Zippleback.
Also implied to have happened to R2-D2, although we never see what it was that pulled him under the surface of the swamp.
And Jabba the Hutt, in various other media if not the movies themselves.
Burt Gummer gets swallowed by a Graboid in the third Tremors movie; he's in an oil barrel at the time, which offers a degree of protection, but he's still looking a little grotty when he's cut free from the corpse.
In a variant from The Bones Of Haven, a giant spider encountered in the sewers lands on Hawk when it's killed. While it didn't actually swallow him, he punches a hole in its descending abdomen with his ax, ends up inside its (mostly hollow) belly, then spends the next couple of minutes hacking his way out.
Happens sometimes in Animorphs. Rachel is once swallowed by a kronosaur, morphs grizzly, and claws her way out.
Also Marco, who gets swallowed in spider morph by a bird and then has to morph out of it.
How one travels by blimp in the Gaea Trilogy. Luckily, blimps' digestive acid has approximately the pH of strong tea; they can only digest food that's been pre-digested and crapped out again by their symbiotes.
Happens on purpose in Leven Thumps and the Gateway to Foo when an Earth Snake eats the gang. They get back out alive. Happens by accident in Leven Thumps and the Whispered Secret when Leven swallows Geth.
During the course of Galaxy of Fear: The Nightmare Machine, Tash and Zak end up in the mouth of a whaladon, and know that being swallowed will kill them. It's a hologram.
On Charmed, the Big Bad Wolf does this to Piper and Grams in a fairy-tales-come-to-life episode. Piper blasts it into a cloud of fur-tufts from inside, and the two are released unharmed.
In the Star Trek: Voyager episode "Bliss," the Voyager crew is led inside a giant bioplasmic creature who deceives them into thinking they are flying into a wormhole that will lead them straight to the Alpha Quadrant. Only Seven of Nine, Naomi Wildman, and the Doctor are unaffected, as Seven and Naomi share no interest in returning home and the Doctor was taken offline by the rest of the crew. They encounter an alien pilot of another ship who was trying to destroy the creature and work together with him in order to escape.
In "Basics, part 2," Hogan was killed at the mouth of a cave where a giant snakeasaurus lived in a lightning-quick Discretion Shot. Later, more of the Voyager crew were attempting to sneak across a cavern where the snakeasuraus slept in a pit. It didn't work. A nameless crewman slipped, awoke the beast, and got Swallowed Whole just like Hogan.
In the Dinosaurs episode "I Never Ate for My Father", Earl, Robbie, and a few mammals get eaten alive by a giant swamp monster, and are still alive, whole, inside its stomach (as it takes a week for a creature of that size to digest its meals).
Many Muppet characters have been eaten whole by monsters over the years. One of the most notable examples being the "Under My Skin" number.
Miniatures of St. George and the Dragon often show George freeing a maiden (unharmed) from the dead dragon's belly.
Chronos swallowed all of his children whole when he found out that one of them would overthrow him the way he had his father. When Zeus (who escaped such a fate by the trickery of his mother) kills him, he pulls his siblings out alive.
When Zeus finds out that he's to succumb to the same fate, he eats his pregnant lover. However, it is their daughter that reemerges unharmed in the end.
Early Mesoamerican artwork suggests that the cultures of the area had a story similar to Jonah. Statues of a man being swallowed by a large fish have been found on archaeological sites.
Some monsters have the Swallow Whole ability. (Purple worms are likely the most notorious creatures who do so.) Victims take damage as they are digested, but can try to cut themselves out. However, "muscular action" closes the hole afterward, meaning that multiple swallowed adventurers each have to cut their own hole. Utterly ridiculous, yes, but it stops players from deliberately getting swallowed and then insta-killing the monster.
Advanced D&D monsters that can do this are the albino wyrm, behir, carnivorous whales, Dinichtys, froghemoth, Tyrannosaurus Rex, giant catfish, giant frog, giant gar, giant shark (Megalodon), manta ray, remorhaz, sea wyrm, verme and wereshark.
Basic D&D monsters with this ability include the caecilia (giant worm), large carnivorous land dinosaurs, giant sturgeon, giant manta ray, giant toad, killer whale and nightcrawler.
The Bag of Devouring is a classic cursed magic item which, while it appears to be a useful Bag of H0olding, actually leads to the stomach of an other-dimensional monster that can drag the user in to be digested alive any time they reach into the "bag".
Tyranid Mawlocs from Warhammer 40,000 tend to do this. And their victims are still alive and conscious while they're being digested.
The Red Terror does it as well. Both in gameplay mechanics and fluff. In fact there is a codex story devoted entirely to the subject.
Rosella from King's Quest IV: The Perils Of Rosella gets swallowed up by an enormous whale. She can escape by climbing back up to the mouth and tickle its uvula with a feather to make it sneeze her out.
Mike in StarTropics is swallowed by a giant whale, but reunited with Baboo, who is relived to see Mike safe and sound, but dismayed they had to reunite in the belly of a whale, of all places. Together they work on escaping the huge beast by building a fire and promptly getting sneezed out.
The monkeys from Super Monkey Ball 2 all get swallowed up by a greedy blue whale. The monkeys later ram its stomach, upsetting the ocean giant, forcing it to eject them from its blowhole.
Some monsters in Science Girls will swallow one of the characters and have to be fought in order to release her. At one point, the whole party gets scooped up together and then has to force the monster to spit them back out.
This is the trademark attack of Pakkun Lizards in the World of Mana series. It tends to make them more of an annoyance then an actual threat, as they usually can't do anything until they spit out their victim, Legend of Mana being the only game where they don't suffer from an immobilizing Balloon Belly as a result of swallowing someone that's generally twice as big as them.
Inverted in the Kirby series - you're the one who swallows the enemies, even if they're bigger than the main character's entire body!
Replacing the Dragon class' usual flying claw strike in Disgaea 3 is their Inside Tour attack, which does this to the target (And potentially a teammate, if the dragon is using the move as part of a Combination Attack, though they're Friendly Fire Proof). The victims literally get pooped out a few seconds after being devoured.
The final raid boss of classic World of Warcraft swallows party members whole throughout the fight. The swallowed party members must destroy him inside out but also try to escape before the stomach acids dissolve you alive.
"Did you see me lay down the law? I AM DA LAWGIVAH!"
The boss fight concluding the Dark Ice Mines stage in Star Fox Adventures involves an enormous reptillian centaur swallowing Fox whole. Once within the cavernous stomach of the creature (illuminated with the light of a Spell Stone), the protagonist must continually assault a dangling mass of tissue before the monster regurgitates him back onto the battlefield.
Banjo & Kazooie get eaten by a gigantic photorealistic..ish dinosaur in Banjo-Tooie. Luckily it just wants the duo to rid its stomach of ulcers in a Mini-Game.
Bowser does this to the Super Mario Bros. in Bowser's Inside Story, and they spend a large portion of the game in various parts of his body. Later, he gets the ability to do this in battle, devouring enemies and leaving them for the bros to fight.
Done doubly so in the Turtle Zone of Super Mario Land 2. The titular turtle swallows Mario, though there's nothing stopping him from just leaving. The last level of said zone is inside a whale.
In the Runescape quest "Deadliest Catch", the fisherman Jones gets swallowed whole by the Thalassus, a giant sea monster. The Player Character feeds the Thalassus some nasty-tasting karambwan fish and it spits him right back out again.
In the CRPG Dragon Lore, the player at one point has to get himself swallowed by a large fish to retrieve a key it ate (Or you can just kill it and gut it. Rather ridiculous since the fish is not a giant, but "merely" eight feet long or so, and is also a pike, one of the few types of fish that do not swallow their prey alive, but rip them apart first.
God of War 3 has the boss fight with Cronos end with him grabbing Kratos and throwing him down his gullet, mockingly exclaiming "Trust me, eating you will be more unpleasant for me!" He has no idea how right he is.
The Rockgagong in Tales of Graces does this to the party, though only because it was agitated by an infestation of parasitic monsters. It ends up spitting them out after Asbel opens a pouch of pepper he unknowingly received from his brother. If you decide to provoke it into attacking you with the Rockggaong Flute that's found inside of it, it'll try to do it to anyone who's standing too close to its head in the resulting fight.
The whole episode is pretty darn hilarious because, for a while, the party had seriously considered "going with the flow" (so to speak) as their only method of escaping.
Both Mega Man X's Launch Octopus and Mega Man X5's Duff McWhalen levels have enemies that do this. It's more inconvenient than harmful, since the titular android can simply blast his way out.
The Xiaolin ShowdownPS2 video game has three levels involving this trope - Dojo's Mouth, Dojo's Esophagus, and Dojo's Stomach. The entire cast is swallowed whole and must fight enemies inside him. Doubles as a Womb Level.
This is Yoshi's trademark ability. While it initially just got rid of enemies (Size rarely being an obstacle), later games would have them transformed into eggs, which could be used as weapons.
Most of the bosses in Yoshi's Island get zapped by Kamek before the fight starts, making them bigger and stronger. For the world 3 miniboss, though, Kamek zaps Yoshi and Baby Mario, shrinking them down to a convenient bite-size for Prince Froggy to eat. You beat the boss by attacking its uvula with eggs you make from other enemies the boss eats.
Played a bit more straight with the King Jellyfish, a boss that introduces itself by engulfing you.
Several Resident Evil creatures will do this to a character, such as Yawn and Neptune in the first game, the mutant alligator in 2, Gravedigger in 3, the Gulp Worm in Code Veronica, the Lurker in 0, and Del Lago in 4.
The T-Rex in Dino Crisis will devour Regina in one bite if it gets in range.
Whether the predators in Kevin & Kell swallow their prey whole or kill and carve them first seems to depend mostly on Rule of Funny.
Two members of The Order of the Stick find themselves swallowed whole by black dragons. Haley is rescued when Vaarsuvius casts Suggestion on the dragon and orders it to vomit, and V deals with being swallowed by casting Shapechange. The results aren't pretty.
Kaz the Jester in Work Sucks is a collector of monsters, so this happens fairly often. He’s invented several methods to get out of those situations,one of which being a pill called "Pukitol”
In Bloody Urban, Shannon (a ghoul) swallowed one of his classmates in the 6th grade because he wanted to assume the other kid's identity. Unlike with most uses of this trope, it's implied that the boy's face was badly burned by Shaz's stomach juices, and when you see him as an adult he still has some noticeable scars.
The team get swallowed by ... something large and aquatic in an episode of Genocide Man.
Giriii: My dad took me whale hunting once. Never thought I'd be swallowed by one.
Jacob: This isn't a whale. Whales don't have card tables, chemical toilets, or crates of MREs.
Girii: It smells like a whale.
The Orbots from Mighty Orbots end up inside Leviathan, a gigantic alien whale. The criminal organization 'Shadow' intent to use the creature flatten the native underwater cities via an implanted Mind-Control Device in its brain. They have to journey inside its vast anatomy to shut down the device, and revert Leviathan back to its normal-self.
In The Garfield Show Garfield is put on trial by fish everywhere for his crimes against them. He's found guilty, and sentenced to Larry. Garfield is naturally confused, until a massive whale named Larry arrives to swallow him up.
In The Simpsons parody of Paul Bunyan, a giant Homer accidentally swallows Lenny. Groundskeeper Willy swims up through the stomach juices to Lenny saying "I've found another exit. It ain't pretty, but it'll do".
In the Super Mario World cartoon, Hip, Hop and King Koopa are swallowed by a giant Piranha Plant which is then eaten by Yoshi. After Yoshi complains of being sick, he spits the Koopas out.
This entire scene is lampshaded by the episode's song, "Rockin' the High School."
One big tree's gonna steal the show, Goin' down easy, Gonna swallow you whole!
Twice on Jimmy Two-Shoes. Once to Lucius, who is eaten by a large sea monster in the Beach Episode. Then done to Jimmy himself in one of the shorts. Both, naturally, make it out okay.
In one episode of The Grim Adventures of Billy & Mandy, Irwin is swallowed whole by a giant alien bug creature. When he turns up alive and rather disoriented at the end of the episode, and they ask him how he got away from it, he says, "Try not to dwell on it too much..."
Hanna-Barbera's Moby Dick episode "The Sea Monster". Tug is swallowed by the title monster and finds that its interior is hollow.
Kenny in South Park was once swallowed whole by a giant reptilian bird.
In The Snorks, the Snorks are swallowed up by a giant Snork Eater that plays hypnotic music that lures its prey toward it. They manage to escape by blowing a giant bubble inside it while Tooter duels musically with the Snork Eater.
And before that, The Smurfs had the title characters on a sailing ship swallowed up by a whale in "Smurfs At Sea". They escape by tearing apart their boat and turning part of it into an escape raft while the rest was converted into a hydraulic lift to keep the whale's mouth open long enough for them to escape through it.
"Man-At-Arms" gets the honor twice in the 2002 He-Man series. Actively struggles against bodily functions pushing him toward the acid filled stomach but the place is still well lit, better than the outside the first time.
In T.U.F.F. Puppy, during a flashback to one of Kitty's horrible birthday parties it's shown that once she ate a mouse magician that her parents had hired, then coughed up a bunch of scarves.
Lemongrab 2 of Adventure Time fame gets swallowed whole three times by his brother, Lemongrab 1. First time around, he loses a chunk of his head and his legs, but the other two times leave him relatively unscathed, and able to literally fight his brother from the inside.
"A Day At The Zoo" from 1939 ends with Egghead inside the lion's stomach, still alive.
In Tex Avery's "Jerky Turkey" (1945), a bear named Joe swallows the pilgrim and the turkey alive.
In Xiaolin Showdown, the episode 'Enter the Dragon' involves Dojo becoming evil for a day, turning into a giant two-headed dragon and swallowing the main cast whole. As Clay tells Omi, "Good thing Dojo never learned to chew his food." They eventually make it out safe when Omi gets sweated out and defeats Dojo in a Xiaolin Showdown.
In the Tiny Toon Adventures episode "Buster and the Wolverine", the wolverine swallowed Babs, Plucky, Hamton, Furball, Sweetie, and the Myna Bird after taking them to his cave, they later managed to escape after beating him up from the inside and playing their instruments knocking him out, then Buster hits his butt with a mallet causing him to spit them out.
On Taz-Mania, Taz often eats Wendell T. Wolf whole. Fortunately for Wendell, Taz doesn't like the taste of Tasmanian wolves, and is quick to spit him out.
On an episode of Inch High, Private Eye, the diminutive detective is captured by a criminal mastermind who also makes robots, one of which he has swallow Inch whole. But Inch manages to bounce his way back up to the robot's mouth, and by using a feather, gets it to sneeze him out. As he comments immediately afterwards, "...[You] can't keep a good man down!"
On an episode of The New Adventures of Huck Finn which combined elements of "Moby Dick" and "Fantastic Voyage", Huck and his friends Tom Sawyer and Becky Thatcher are swallowed by a giant whale while trying to escape a mad Ahab-like sea-captain who was trying to force them to help him kill it. The whale also swallows the captain when he falls overboard while trying to harpoon it, and the kids go on a strange and perilous journey through the insides of the beast, trying to evade the villain and find a way out, which they eventually do through its blowhole, leaving their pursuer to be presumably digested or trapped forever.
In the Steven Universe episode "Giant Woman", Steven (and a goat) getting swallowed by a giant bird prompts Pearl and Amethyst to do their Fusion Dance to save him (after he'd been begging them to do it for the whole episode).
In a Rupert episode "Rupert and the Missing Snow", Rupert, Polar and Will were adrift on a small iceberg only to be swallowed up by accident by a massive whale. She was suffering from a terrible toothache for mistaking the North Pole as a piece of candy. They were fortunately blown out her blowhole.
The trope happens in Real Life in regard to large frogs and toads. Unlike snakes, which crush their prey either by strangling or during eating it whole, the frog or toad swallows the prey (which may be anything from insect to mouse to smaller frog) in a fraction of a second, before the hapless animal even realizes what happened to it (it has to be filmed in slow motion for human eyes to discern). This means the prey is alive and conscious for at least a second before digestion begins.
Large constrictors (pythons and boas) have been filmed eating small, weak prey live rather than spend the effort to subdue and kill it.
Taken to the extreme by the pelican eel, a deep-ocean predator that's pretty much a gargantuan maw with a stringy little tail hanging down from it. It pretty much has to swallow prey whole, as its teeth are tiny and its jaws built to engulf, not bite.
From Pelican eels to Pelicans. In fact a lot of bird species that live on a fish diet have to swallow the critters whole. Pelicans that live in or close by human settlements will even go for pigeons◊.
Most advanced species of predatory bony fishes feed this way, using specially-adapted jaw articulation to expand their mouths so rapidly that prey is sucked inside.
In fact, outside of mammals, most carnivorous vertebrates will swallow huge chunks of flesh in a go rather than chewing it, and thus relatively small prey often goes down in a go. Relatively, because sauropsids (reptiles incluiding birds) have wide and thick walled esophagus, and thus stuff that doesn't seem to even fit can go down.
Averted with carnivorous arthropods, annelids and mollusks: Due to the fact their brain develops from a ring surrounding their digestive tube rather than from the endpoint of a dorsal cord, they have to swallow very small chunks of food, or they risk being brain damaged.