This is lampshaded in Scooby-Doo and the Witch's Ghost, when both Shaggy and Scooby eat a ton of food and put on a lot of weight... but they later drop the weight after running away from the Hex Girls whom they think are witches.
In Scooby-Doo and the Monster of Mexico, it is stated that Shaggy does have a high metabolism.
In an episode of Scooby-Doo! Mystery Incorporated, Daphne actually manages to out-eat Shaggy and Scooby, due to having to wait over two hours for a table at a restaurant and then getting dragged away to a mystery as soon as one was free.
Odd Della Robia in Code Lyoko frequently cleans the lunch trays of his closest friends, despite maintaining a svelte frame.
The nurse believes he might have a high metabolism that could explain it.
Amusingly in the scene where the high metabolism is discussed, the nurse proceeds it by asking if Odd eats enough, prompting Jeremie to quip "By enough, do you mean 'more than a baby elephant'?" which in turn makes the other boy in the room snicker.
Futurama's Nibbler, who converts the calories into super-dense spaceship fuel. And the rest of the Niblonians, for that matter. The Feast of a Thousand Hams, anyone?
Mindy, a one-shot character from The Simpsons, was almost as fond of junk food as Homer was. How she maintained her sexy figure was a mystery.
Like his comics counterpart, The Flash from Justice League eats big to fuel his incredible metabolism, as does Kid Flash of Teen Titans.
We've seen Cyborg and Terra eat monstrous amounts of food in Teen Titans, though in Terra's case it was implied she hadn't had a decent meal for quite some time.
Kid Flash passes a quarter of his debut episode eating food stole to his captors. When he broke out and devastated their headquarter he also raided the kitchen. It's made clear he needs it to keep his speed: Madame Rouge manages to defeat and almost capture him by attacking continuously until he tires.
Jimmy and Jerry Gourd of VeggieTales. In their introductory episode, they eat an entire asteroid. (It was made of popcorn, but still, that's a lot of popcorn.)
Bink from the Chip 'n Dale Rescue Rangers episode "Adventures in Squirrelsitting". She is a toddler, yet she sucks an apple that's larger than herself empty within mere seconds, including the core, and she's still hungry.
Buster from the Arthur TV series. He will eat virtually anything, even tomato cookies made by Lethal Chef Grandma Thora.
A play in "The Ember Island Players" that covers the events of the main characters' journey makes Sokka out to be a Big Eater. Though despite the fact that the play exaggerated everyone's traits, Sokka does seem to like food more than the other main characters, as seen when he couldn't go a moment without thinking about food in the episode "The Southern Air Temple".
The little rodent Rufus once ate two months of his allowance, in just one meal.
Ron Stoppable is a pretty big eater as well, played to extreme lengths during a special episode about fatness.
Kim herself once ate an entire plate of Nachos in one second, in an effort to bond with Ron and his new friend Felix when she started feeling left out.
Kim: Sorry if I've been acting totally random lately. Ron: You mean about the jealous thing with Felix? Kim: Was it that obvious? Ron: Kim, you ate all his nachos.
As the Animaniacs theme song states, "Wakko packs away the snacks". While his siblings Yakko and Dot normally go after the sweet stuff, Wakko's the type to gobble up everything in the refrigerator, and then eats the fridge itself!
Captain Caveman. He once ate a whole tray of bronto burgers... Including the tray.
Philly Phil of Class of 3000 eats far more than his skinny frame would suggest, such as downing half a pizza (his friends don't flinch, so he must do this quite often), and has even bordered on Extreme Omnivore.
Kam:(after Phil has eaten his 101st donut... with a candle on it!) Don't you chew? Phil: Depends.
GIR from Invader Zim, which is made all the odder by the fact that he's a Robot Buddy. The only time he ever gets fat from it is in one episode where he started mugging kids for their Halloween candy and ended up fattening up to an extreme size.
Chester, Mark, and Grippulon in The Fairly Oddparents. Chester especially when he became Matter Muncher Lad (an Expy of Matter-Eater Lad).
On The Real Ghostbusters, the team keeps a ghost named Slimer at their headquarters (the same one they encountered at the hotel in the movie, apparently) who has an unlimited appetite, and can eat anything that edible. He even gladly gobbles up food that most humans find unpleasant, like hospital food and spoiled food. (He once ate the contents of a lunchbox that Venkman had lost when he was ten years old.) Of course, the team tends to encounter other ghosts with appetites like this, from time to time.
Basically the one joke of Billy Boy. Tex Avery still manages to get a lot of mileage out of it.
Che the dog from The Goode Family will devour any smaller animal that comes near him because he refuses to eat the vegetarian dog food that his owners feed him, a great example of this is in the episode "Goodes Gone Wild" in which a swarm of squirrels infest the school and Gerald brings Che along because he doesn't want him to fight with Gutterball the marsupial he devours one that gets within reach of him and upon learning that the school is covered with them he licks his lips with delight and breaks his chain, at the end of the episode the swarm is gone and Che is lying against a tree with a huge swollen belly.
An episode of Jacob Two-Two featured a team of police officers attempting to track down what they thought were "grocery store bandits". After discovering the eponymous protagonist and fellow grade-school friend outside a grocery store at night, the skinnier officer comments that "It's the little ones you have to look out for" right before downing half a box of donuts.
Doofensmirtz once invented an inator which gave you a bottomless appitite for a few minutes, but did so by speeding up your metabolism so much you were burning through the food as fast as you ate it without putting on any weight.
Also seen in Snails, a young unicorn colt whose head is bigger than his body. One bite and most of a chocolate cake is history.
Spike the dragon can chomp down a bowlful of gemstones in one gulp.
Applejack also can certainly pack away the chow. Justified due to all the work she does around the farm.
Soarin', of the Wonderbolts, literally eats like a horse.
Could be justified, since flying around at fast speeds would burn up a lot of energy.
Spitfire: Always hungry after a show, eh, Soarin'?
In "Ponyville Confidential", Princess Celestia is caught on camera eating a huge cake with her hooves.
When Twilight Sparkle first meets Applejack, she eats enough of the family's cooking to give herself a Balloon Belly.
The title character Chew Chew from the FamousStudio cartoon Chew Chew Baby, a pygmy cannibal who over the course of the cartoon devours six people, two of them in a single bite. The cartoon is cited as a source of Nightmare Fuel for some people.
Mac from Foster's Home for Imaginary Friends almost always averts this trope, until he's given sugar. Once he has the slightest bit of sugar, he'll be eating anything he finds that's sweet. Where it goes, on the other hand, is never found out, though he does burn a lot of energy running around like a maniac on his sugar high (and he's a bit more Puni Plush than the other human characters).
Similarly so, Frankie and this trope usually never meet, but in "Cookie Dough" it becomes clear that she cannot hold herself together when Madame Foster bakes cookies. Once Bloo starts making them for profit, she demands boxes with up to twenty dozen cookies before asking if there was a limit, and every single scene with her after that showed her stuffing her face. The end credits show her lying on her bed with empty boxes and empty milk jugs all around her and her body severely bloated — and she just keeps going.
In the PBS kids show Dragon Tales, it's quite obvious that Ord has a stomach bigger than himself as he is often seen eating a large number of food from time to time. (Yikes...!)
Ed from Ed, Edd n Eddy will eat pretty much anything, up to and including his mattress. It's even worse when he starts sleep walking...
Rigby from Regular Show once ate so much junk food that his body quit on him.
The eponymous character of Mr Bogus. In fact, the opening credits even showed him devouring two out of three entire scoops of ice cream (chocolate, vanilla, and strawberry), missing the third scoop in the process.
His younger cousin Brattus will also take on this trait at times, to the same extent as that of Bogus himself.
Wally West/Kid Flash in Young Justice, like his Teen Titans counterpart above, needs to eat a lot because of his extremely high metabolism. His costume has a snack compartment so that he can refuel on missions.
In Justice League, Wally West/The Flash (this seems to be a common trait of all versions of the character) also needs to eat a lot due to high metabolism. He actually complains about this in "Hearts and Minds" when he has to eat an (judging by his and Kilowog's expressions) alien vegetable that tastes terrible because someone with his metabolism can't be picky.
Probably Eustace from Courage the Cowardly Dog. He constantly demands that Muriel cook for him, and his hunger saved Courage and Muriel from Katz once.
Buzzbee on The Hive can bee this at times, and occasionally it gets him in trouble. He does look a bit roly-poly, but only beecause that's how the characters are drawn; he doesn't really look any different from any of the other children in terms of size.
In Hanna-Barbera's version of The Little Rascals, Porky is almost always shown eating a sandwich or some such thing. In one of the 30-second cartoons, Darla asked Buckwheat how many meals Porky eats in a day. Buckwheat said just one—from the time Porky rises in the morning until he goes to bed at night.
In Dan Vs., Chris has this BAD, to the point that he hides food IN DAN'S APARTMENT! The first episode of season 3 implies that it's at least partially due to over-repressing his anger
In one episode, we are informed that he once SLEEP-ATE a pair of SLIPPERS, with SHAMPOO as a dip, making him an Extreme Omnivore as well.
The Insecticons of The Transformers can and will eat anything, from a field of grain to the shield plating on a military base. They become especially dangerous when allowed to feast unchecked since the energy they gain allows them to generate a near endless supply of mindless clones that are just as hungry as they are.
Chowder is possibly the biggest eater ever conceived, to the point where it's his defining character trait. On several occasions, he's doubled as a Bag of Holding, able to eat large objects — up to and including an entire fair booth — and spit 'em out later.
Homer Simpson. Tis no man, 'tis a remorseless eating machine! As a result, Springfield's "All You Can Eat" restaurants fear Homer greatly. But many food vendors singlehandedly make their entire living, and pay their childrens' college fees off of just Homer alone, making him a valuable commodity to others. According to Homer himself, "it's glandular."
Police Chief Clancy Wiggum's round body says it all. Although mostly known for his sweet tooth, he's open to a wide range of food including some pretty exotic stuff.
Comic Book Guy actually trumps both of the above in terms of sheer size, though this is due to being perhaps the most lethargic man in all of Springfield. And in Springfield... THAT'S an accomplishment.
The German foreign exchange student Uter is pretty much solely defined by his absolute lust for all things chocolate.
Not usually known for his eating habits, there has been some times where Bart has overindulged to great extent.
In fact, there is one episode where Springfield breaks the record for being America's Fattest City. (Homer is rather proud of this accomplishment, exclaiming, "In your face, Milwaukee!" but Marge is embarrassed by it, and puts the family on a diet.)
When Kenny is brought Back from the Dead as a zombie in "Pinkeye", Cartman steals his school lunch and eats it along with his since he's no longer being responsive.
In "City on the Edge of Forever", Eric eats an entire chocolate cake that could theoretically feed the entire school bus for about... a day or so, at least. Which they happen to get trapped inside as it gets stuck on the edge of a cliff.
During the beginning of "The Death of Eric Cartman", Eric eats all the skin off of an order of extra crispy KFC for all four of the boys.note This results in one of the mere two instances in the entire series where Kenny actually cries (the other being "The China Problem"). He ends up rupturing his spleen and clogging the toilet when defecating it, causing him to actually believe himself dead.
Monterey Jack can (and loves to) eat incredible amounts of cheese.
Zipper falls into this category, too. There is at least one scene in which he tosses an entire apple core almost twice his size down the hatch.
Fizz from Get Ed orders herself three burgers, a basket of fries, a basket of onion rings, and a basket of pickles... and slaps Loogie's hand away when he attempts to take a pickle. Apparently, she intends to eat all of this by herself (her teammates don't even blink, so she must do it pretty regularly). However, she's got a little bit of pudge around her midsection, especially in comparison to her trim teammates.
The Flintstones: Fred Flintstone is known to polish off Bronto-Burgers with little effort.
The Replacements: Dick Daring is so bad he ate forty pounds of Ice Cream so he could beat his record by one pound.
Heffer Wolfe from Rocko's Modern Life. He once devoured the entire contents of Rocko's fridge when Rocko wasn't home because he [Heffer] thought it would spoil.
In another episode, Heffer saved his snack money for a week, and bought a motorcycle with the savings.
Gina Lash of Angela Anaconda is a big fan of food, to the extent she once started a protest about a flavor of her favorite gelatin ("Jiggly Fruits") having its recipe changed, and as a result of her constant eating is quite pudgy, particularly compared to the stick-thin Gordy Reinhart or, indeed, any of the other kids she hangs out with.
Hank's fat son, Bobby Hill, in King of the Hill. He once ate a 72-ounce steak in 37 minutes.
Though in an episode, Bill enters a hotdog-eating contest because he's a fast eater, and then near the middle, Dale, the skinniest of the group, is sick of all the praise Bill gets for it and while mocking him manages to beat Bill in an eating practice round.
It's worth noting that Bill discovered he could be a competitive eater by eating a whole platter of hot dogs at a friendly barbeque in about three minutes without even trying. His neighbors, watching, reacted with disgust than he typical cartoonish amusement usually seen with this trope (aside from Bobby).
Another episode when Bobby attends a military camp he ate hoards of leftover meals as a punishment by Cotton Hill when he took control.
Owen from Total Drama, so much so that in ...Action he ate an entire feast in minutes without realizing it was prop food.
Captain Huggyface in WordGirl definitely qualifies, as he is used to nullify all the attacks of the Butcher and Chuck the Evil Sandwich Making Guy. He also is shown eating large amounts of ice cream during scenes, and whenever they come across some type of food, Huggy always has to look into it.
Donald Duck's cousin Gus from the cartoon Donald's Cousin Gus, who comes to visit Donald and through the episode devours all of Donald's food without leaving him a single crumb. Many Youtube commentators have expressed their desire to strangle the gluttonous goose, which might explain why he has never appeared in any other short after this one.
Codename: Kids Next Door: Numbah Two. Comes in really handy since one of the villains is Gramma Stuffum, a crazy lady obsessed with force-feeding children healthy (read: disgusting) food, and in command of legions of sentient meals.
On Garfield and Friends, besides Garfield himself, Jon, in one episode receives a visit from his Uncle Ed who proceeds to eat him out of house and home. Finally, Garfield, who can't even get a single bite in edgewise, decides to call Jon's Aunt Edna to take him back home and put him back on the diet he was supposed to be on.
Winnie the Pooh. His hunger for honey knows no bounds.
On Goof Troop, Pete is shown to be this; his eating habits are the focus of three episodes and we often get to see him scarfing down large amounts of food quickly. There was a joke in one of said episodes where he ate six powerbars in one sitting (that were supposed to be two days' worth), and in another he ate a gigantic breakfast and was then patted down for extra food he was hiding in his clothes—which turned into The Long List. His son, PJ, is also said to be this on several occasions, by himself and others, though it is rarely actually shown.
An episode of the 80s series "The Fairy Dogmother" shows Brattina as this in a Compressed Vice moment where she's at a party and ignoring her date in favor of the buffet table.
Grumpy Bear of the Care Bears certainly enjoys his food in any version he shows up in. He isn't necessarily any bigger than the other bears, but walking cuddly bears aren't skinny.
Crunch in Mighty Orbots was specifically designed to be this. Namely, after from his destructive value, his primary function to convert anything he eats as energy and enable it to be a power source for the Orbots' united form.