In the Kim Possible episode "Hidden Talent", Ron Stoppable purposely performs the trope using hot sauce for a talent show.
Averted and a lampshade hung thereupon by The Simpsons in "El Viaje Misterioso de Nuestro Homer;" as Homer eats bowl after bowl of red-hot chili containing "insanity peppers" with no ill effects, Dr. Hibbert remarks "By all medical logic, steam ought to be pouring out of his ears." Adds Krusty, "His ears if we're lucky." He coated the inside of his mouth with wax for protection from the pepper's heat, but soon after swallowing they do cause him to hallucinate for a whole night.
Played straight earlier in the same episode, as Homer's uninsulated tongue glows neon red when it comes in contact with a Guatemalan Insanity Pepper. It evaporates anything less than an armful of liquid on contact.
In the My Gym Partners A Monkey episode "Have a Joyous Little Animas", eating a plate of wasabi causes Adam to breathe fire through his nose.
In A Garfield Christmas Special, Grandma spikes Mom Arbuckle's sausage gravy with chili powder ("Who am I to tell you how to make gravy? The Green Country gravy champion, that's who!"), and Garfield ends up spewing a gout of flame as a result. ("Perfect.")
An early example comes in the Walt Disney cartoon Donald's Nephews (1938), when Huey, Dewey, and Louie feed Donald Duck a slice of pie that's been doctored with mustard.
Lampshaded in American Dragon Jake Long where after eating some super spicy fries, Jake has to breathe fire to cool his mouth down!
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In an episode of Xiaolin Showdown, Dojo (a dragon) needs two bottles of Clay's family-recipe hot sauce to breathe enough flame to beat the Sapphire Dragon. Normally he can only breathe small soot clouds. (He was clearly a little rusty, having not done it for several centuries.)
A variation is played in Saludos Amigos, where Donald drinks a glass of Brazilian cacha? (saying it's an extremely strong sugarcane spirit is a very great understatement) that causes him to spout flames. Josť then uses Donald's flame breath to light a cigar.
Chowder once ate a bushelful of hot peppers that caused him to breathe fire every time he opened his mouth. He had to live with fire-breathing dragons until the effect wore off.
In the Sushi Pack episode "Red Hot Chili Planet," Ben had to pass along a message from Wasabi to the others, but since Wasabi speaks "mustard", Ben has trouble getting the inflection right. Ikura suggests he drink some hot sauce to get it right, and with one drop, Ben is breathing fire (and starts speaking "mustard")!
In one episode of Tiny Toon Adventures, Elmyra accidentally feeds Dizzy Devil a can of hot chili instead of dog food. Cue the eyes watering up, breaths of flame, then running to the shower to put out the fire.
In a high-quality restaurant, dog eats the sample chili peppers which cause Cat to belch out flames. This catches his dream-interest who happened to be in the restaurant, whom he entertains by fire-broiling her steak. This backfires later when he accidentally turns her pet dog into ashes.
When CatDog get trapped in the reality of their favorite movie, Cat pours Dog's favorite candy snack, Red Hot Lip Smackers, into his mouth and uses him as a pistol to burn the enemy starships.
A major problem for Cat whenever Dog uses too much hot sauce on his tacos. Because they're conjoined, the hot sauce passes from Dog's stomach to his, causing him to belch fire out of his mouth.
Done realistically in one of the Rugrats' earlier episodes, "Waiter, there's a Baby In My Soup!", where Stu has no choice but to bring Tommy with him to an important business dinner with the president of Mucklehoney industries (a toy factory). Tommy wriggles out of his baby crib under their notice, and wanders into the kitchen where he pours garlic powder, pepper, and hot sauce into a chef's soup prepared for the president. Upon sampling the concoction, the president struggles all over the floor, gasping for water while Tommy returns inside a bowl of spaghetti.
In one episode of My Little Pony: Friendship Is Magic, Twilight Sparkle accidentally drinks some hot sauce, and though her face does turn red with a kettle-whistle effect, it's her mane, not her breath, that turns to fire.
Even Pinkie Pie herself falls victim to this; she breathes fire for a moment after literally tasting a rainbow in "Sonic Rainboom". The fire even turns multiple colors. Keep in mind that Pinkie is seen eating a cupcake drenched in hot sauce in the pilot episodes.
One episode of Men In Black featured Agent Jay consuming alien salsa, resulting in him temporarily developing fire powers.
This actually happened to Iggy in the The Little Lulu Show episode, "Tiny Tots Syrup", after eating some apparently spicy candies in order to get the terrible taste of said tonic out of his mouth.
When Heffer eats Hot Tamales in the Rocko's Modern Life episode "Spitballs" and is about to do this, Rocko points him to the opposite direction. The duck that was sitting next to him becomes a cooked goose.
Taz-Mania: Happens in "Francis takes a Stand" when Francis switches Taz's lemonade recipe for a hot sauce recipe. Taz's resulting fire breath scorches Francis like a flamethrower. When Francis tries to turn the tables on Taz and takes a swig of the lemonade/hot sauce, his fire breath acts like a jet engine and propels him into a cliff.
This shows up in the first claymation short shown during the intro before the episode "Shop Around The Clock", where Bogus attempts to put some pepper on tomato soup, but there isn't any pepper. This prompts Bogus to eat an entire container of ground pepper without any ill effects, but it's when he takes a taste of the tomato soup that he starts blowing fire.
Averted in the third act of the episode "Babysitting Bogus", as while Bogus does inadvertently suck up a bowlful of chili peppers, he doesn't turn red in the face or breathe fire as he just has a spastic reaction to the spiciness of the peppers.
Other metaphors are used in Ed, Edd n Eddy when the trio tastes Eddy's Brother's Armenian secret hot sauce. Ed's head resembles a burnt match, Edd has steam come from his ears and under his hat, and Eddy's hairs act as fuses for his head to explode.
In an episode of Celebrity Deathmatch, Flea of the Red Hot Chili Peppers does this intentionally during his match with Kenny G., he eats some peppers (red, naturally), which turns his breath into a flamethrower.
Happens to Pete in the Goof Troop episode "Calling All Goofs" after he gets a sample of Aunt Goofelia's chili.
The result of eating the super-hot chilies in the Camp Lakebottom episode "High Plains Garbage Eater".
This happens to Paw Rugg in The Hillbilly Bears cartoon "Going Gopher" after he dipped some turnips in spicy mustard to try and get rid of a gopher, after seeing it have no effect on the gopher he tries on resulting in this.
Shockingly doesn't happen too often in Extreme Dinosaurs, given how much they like Mexican food. One time T-Bone chugs a jar of hot peppers and smoke streams out his nostrils, and even after he stops smoking his breath is still hot enough to melt ice.
Adventure Time: Happens to the Earl of Lemongrab in "Too Young" when he gets fed Bubblegum's incredibly spicy cleaning potion.
Steven Universe: In "Joking Victim", Steven gives Lars a donut covered in fire salt that results in him spewing fire all over the city.