Mutagenic Food

""You are what you eat" said a wise old man,

Lord, if that's true I'm a garbage can."

- Victor Buono, "The Fat Man's Prayer"

"You are what you eat", as the saying goes. In fiction, this is often taken literally, with a character eating something that causes them to transform into whatever it was they just ate, or the creature it came from (for example, a character may start growing feathers after eating a chicken egg). Can be a source of Nightmare Fuel when used in a children's show.

This is often given some sort of Hand Wave in that the food was genetically modified/exposed to radiation/infected with The Virus/of alien origin/past its use-by date.

This trope may also apply to abilities and behaviour associated with the food source, for example, eating brains may supposedly make one more intelligent, or eating a beef patty may make them start mooing and eating grass.

Note that this differs from You Are Who You Eat, in that the latter trope is about characters who can do this with their food as an inherent ability. This trope is for when the food itself has these special properties.

A newly-transformed sentient pile of food will often discover that it tastes delicious. See also: Cereal Induced Superpowers. A Sister Trope of May Contain Evil. Can occur because of Tampering With Food and Drink.

Anime and Manga

 * Wapol from One Piece can do this thanks to eating the Munch-Munch Fruit (Baku Baku no Mi).

Literature

 * In Gelee Royale, a short story by Roald Dahl, the eponymous substance.
 * In Stephen King's short story Grey Matter,.

Live Action TV

 * Doctor Who:
 * In the serial "Delta and the Bannermen" a character called Billy intentionally eats some "royal jelly" so he can turn into an alien to be with the Cute Alien Girl he has fallen in love with and repopulate her race with her. And they lived Happily Ever After.
 * In "Planet of the Ood", Ood Sigma slowly turns Halpen into an Ood by spiking his hair tonic.

Film

 * In John Carpenter's film The Thing, even a single cell of the title monster can convert a living creature into a Thing. One of the scientists suggests that everyone prepare their own food and eat out of cans so a Thing can't contaminate a human's food with itself.

Stand Up Comedy

 * Bill Cosby named a book I Am What I Ate...and I'm Frightened!!!

Video Games

 * A character in Chrono Cross ("Funguy") eats a special mushroom that transforms him into a half-human, half-mushroom person.

Western Animation

 * In Evolution: The Animated Series, Wayne ended up spending the series mutating into a new form Once Per Episode after accidentally eating one of the alien cells in the first episode.
 * In an episode of The Powerpuff Girls, a boy transforms into a giant glue moster after eating radioactive glue.
 * In the Courage the Cowardly Dog pilot "The Chicken From Outer Space", eating alien eggs causes Eustace to transform into a monstrous chicken man.
 * The Magic School Bus showed a Real Life example with carrots. Arnold ate nothing but carrot-based snacks for days and turned orange.
 * When Silkie, the Teen Titans' Team Pet was introduced, he ate some of Starfire's alien zorkaberries, which promptly turned him into an unstoppable (though still cuddly) behemoth.

Real Life

 * Some opposers of GMO food fear this is true whenever food includes "mutations" (or even "DNA"). Mutations however happen spontaneously in all living organisms, allowing for such things as natural evolution.
 * There could be a infinitisimally small chance that not all the vectors used for transgenic modification were integrated into the nuclei of the GMO, but the stomach produces enzymes that break down DNA (which is why Jurassic Park is full of it).
 * Eating too many carrots, or anything else with beta-carotene, can cause your skin cells to absorb the pigment, causing you to turn carrot-coloured. Drinkers of Sunny Delight have also suffered this - Bonus Points for the story being reported just as an advert showed a snowman drinking the beverage and turning yellow as a result.