A Graphical Trope common in Zany Cartoons. If someone swallows something large, his body will deform to accommodate it, taking the shape and size of the object.
Bob makes a gigantic sandwich, much bigger than his head. He then defies physics and shoves the entire thing in his mouth at once. His head then deforms and becomes the exact same shape as the sandwich. He then swallows and the sandwich shape travels down his neck, until it reaches his stomach where it is then digested.
Alternatively, something may be thrown at Bob at sufficiently high speeds that it lodges itself in his mouth. His head again deforms to accommodate the object. He then reluctantly swallows, and the deformation travels down his throat.
Compare Balloon Belly, Traveling-Pipe Bulge and Impact Silhouette. Contrast with Hammerspace.
The Little Prince opens with the narrator recalling how, as a child, he drew a picture of a snake who ate an elephant whole. The grown-ups think it's a hat and chastise him for wasting time drawing silly pictures.
This happens to a snake that swallows Guybrush in The Curse of Monkey Island. We can see the outline of Guybrush standing inside the snake, and he's able to pick up things that the snake has also swallowed.
A variation shows up the Zero Punctuation review of Rise of the Triad where Yahtzee shoves a massive ocean liner piston up the butt of an annoying voice actor, big end first, who's entire body takes on the shape of said piston.
Used frequently on Tom and Jerry, usually when Jerry ate something bigger than he was.
Often appears with Jerry's Big Eater nephew Nibbles.
Tom has also been known to swallow whole Sandwich Towers in one sitting, stretching out his neck in the process.
An episode of Chip 'n Dale Rescue Rangers has Monterey Jack unwittingly eating a piece of dehydrated cheese. When it rehydrates in his stomach, he's comically stretched out into a large brick shape.
On The Simpsons, the school snake is seen crawling with some kid-shaped lumps, one of which is Milhouse (and according to the Springfield Elementary School charter, the school isn't responsible for Milhouse getting eaten by a snake — or Bart dying of appendicitis).
Another episode has Patrick eat a patty whole, then force it down. The patty is visible all the way (pictured).
Squidward has also had the thrown version thrust upon him, as SpongeBob makes Krabby Patties too fast and they all end up flying down Squidward's gullet.
Squidward also has his clarinet shoved into his mouth, and his head is stretched out to accomodate the instrument.
In "Wormy", Sandy shows SpongeBob and Patrick her pet snake, which has a mouse-shaped bulge.
One episode of 2 Stupid Dogs, the big dog somehow gets himself caught in a tennis ball pitching machine and is turned into the size and shape of a tennis ball. The small, ball-obsessed dog swallows him. The big dog reforms inside the small dog, causing the small dog to take the shape of the big dog.
In the Tex Avery cartoon, Billy Boy, the little goat swallows a tire whole and takes its shape, including the hole in the center.
In the cartoon Devil May Hare, Bugs feeds the Tasmanian Devil an inflatable raft disguised as a pig and inflates it inside him, causing him to take the shape of the raft.
In Yankee Doodle Daffy, as Daffy enthusiastically pitches his young protege Sleepy La Goon to talent agent Porky, the junior genius sits on the couch, stuffing a huge lollypop into his face, distending his head...as he twirls it around in his mouth, his head shape follows it.
In Steamboat Willie, Mickey can't get a cow strapped to a crane for loading because it's too skinny. He feeds it a whole haystack to fill it out, which also deforms the head and neck as it goes down.
On The Ren & Stimpy Show, Ren eats dehydrated horse meat, which then rehydrates inside him into the shape of a whole horse.
In the Droopy cartoon Outfoxed, a fox gives Droop a bone with dynamite inside. The other dogs rush him and take it from him. As he asks each dog who has the bone, each one shakes his head no, including the dog who took it, who clearly has a bone-shaped lump in his mouth... until it explodes, leaving the dog with no mouth at all.
In yet another Droopy cartoon, The Three Little Pups, the Big Bad Wolf tries to get Droopy and his brothers by sucking them out with a straw (it's Tex Avery, what do you expect?) and sucks up their televison set by mistake. He opens up his shirt, exposing a TV screen on his stomach. (Later we see the TV back in the pup's house, with Droopy telling the audience "Now don't ask us how we got the television back.")
On Ed, Edd n Eddy, the characters like to suck on jawbreakers that are bigger than their own heads, appearing as enormous round lumps on the side of their faces.
In "Little Ed Blue", Edd tries to cheer Ed up by having the latter blow the candle on, for some reason, a roasted chicken. Ed's response? He shoves the chicken into Edd, making his stomach shaped like it.
In another episode, Eddy convinces Ed to eat his mattress. Edd walks in on Ed partway through the process, his entire body deformed around one half of the mattress.
One Pink Panther cartoon had Pink so hungry that he decides to fold up the background and eat it. It then unfolds inside him until the entire screen is covered in pink.
On Mike, Lu & Og, Lu swallows whole several jawbreaker-like candies called Jujubombs, homemade by Mike and Og to be jumbo-sized.
Happens occasionally in Animaniacs when Wakko eats something.
Beany And Cecil - convict Dishonest John gets a birthday cake full of tools - but the guard makes him eat it all up in front of him. Cue wrench, hammer, and saw-shaped lumps in his throat dropping into his gut with appropriate tool sound effects and a jaunty "Happy Birthday To You".
The claymation short shown at the end of the episode "Class Clown Bogus" had Bogus devour an entire banana in one bite, taking on its shape.
Happens in the third act of the episode "Et Tu, Brattus?" to a piranha after it eats the cocktail weenie that Bogus offers it, leaving its body in the shape of a cocktail weenie.
Happens twice to Brattus in the second act of the episode "Beach Blanket Bogus", the first time when he eats an entire hamburger, and the second time when he eats an entire pretzel, which briefly leaves a pretzel-shaped bulge in Brattus's stomach.
At the beginning of the second act of the episode "Bogus To The Rescue", Bogus, after coming up from one of the floor tiles in the bathroom, eats an entire chocolate ice cream cone in one bite, with the back of his head briefly taking the shape of the ice cream cone.
Though you can't really tell what the snake ate, just how big it was. A snake that ate a rat wouldn't appear much different from a snake that ate a bird the same size as the rat.
Certain deep-sea fishes play this trope straight, due to their highly-expandable guts. Not only that, but some have so little pigment in their own tissues that whatever prey they ingest is plainly visible through the distended belly wall.
The Japanese Giant Salamander swallows its prey whole and alive. It can be seen moving around in its stomach. That's quite a way to die, digested alive in a stomach.