Animals (including humans) have a specific set diet they rely on to survive. We eat certain foods we need to survive and avoid things that we consider either inedible or poisonous.
But, what if an animal is turned into a monster? In the world of fiction, the monster's diet often changes to further illustrate said transformation. A normally herbivourous animal may decide to partake in fresh meat
after becoming a monster. Or, an already carnivorous animal might decide post-transformation that human beings in particular are especially tasty. And, then there's the animals that mutate into monsters that eat pretty much anything (And we do mean anything
Note: This only applies to humans/animals that have changed their diets due to mutatation of some sort. Giant monsters that have the same diet pre or post mutation do not count. Neither do non-mutated characters that just decide to change their diet for some reason.
Can sometimes lead to Horror Hunger
- Vampire stories in general fall under this. Normally, humans don't dine on blood. However, once they become a vampire, it pretty much becomes the main (if not only) part of their diet.
- Werewolves. A good portion of werewolf stories involve the monster developing a craving for large amounts of raw meat as a sign that he/she has been cursed.
- In their transformed state, werewolves were often depicted having a taste for people.
- While not necessarily monsters, many different incarnations of the Teenage Mutant Ninja Turtles depict the titular turtles having a love for pizza.
- The whole mythos of the Wendigo pretty much centers around this. Basically, transforming into one causes the victim to have an insatiable taste for human flesh. And, the more a Wendigo eats, the bigger it gets.
- It sometimes varies as to how the diet change causes the transformation (if it causes the transformation at all). Sometimes just thinking about eating people turns you into one, sometimes just tasting human flesh causes it, and sometimes both killing and eating a human causes it. And that's not including the myths were simply encountering a Wendigo can cause you to become one. Either way, anyone who becomes a Wendigo is basically going to switch their diet to people-only.
- There was a My Little Pony: Friendship Is Magic/Megas XLR crossover Fan Fic called "My Little Megas XLR" which involved Coop being turned into a pony upon entering Equestria. One chapter focused upon Coop realizing that he could never eat any sort of meat ever again, leading to a major rampage which included biting Fluttershy's chickens. Thankfully, the Mane Six managed to wean the guy off of meat while still maintaining his absurd levels of Big Eater
- Night of the Lepus features bunny rabbits that have developed a taste for human flesh after being mutated into giant monsters.
- Zilla from the 1998 remake of Godzilla is a mutated marine iguana. Marine iguanas are herbivors, but Zilla's species dines primarily on fish.
- Godzilla himself from the Japanese films feeds off of radiation, and Junior has been depicted eating leaves. Pre-mutation, Godzillasaurus is a carnivore. Feeding on radiation makes some sense since Godzilla is radioactive, but there's no explanation as to why Junior dined on veggies.
- There is a scene in Underworld: Evolution where the newly-turned vampire/werewolf hybrid Michael tries to eat normal food, only to throw it all up moments later, because he can only feed on blood now.
- A variant occurs in the film The Flight of Dragons. After accidentally merging with a dragon named "Gorbash" (due to a wizard's spell gone wrong), Peter must learn how to be a dragon (since it's now his mind controling Gorbash's body). One of the first things he learns is that a large part of a dragon's diet is limestone (it helps generate their fire breath).
- Occurs rather disturbingly in the 1986 remake of The Fly. Due to his transformation, Seth Brundle soon learns he cannot digest solid food. Like normal flies, he has to vomit a digestive enzyme onto his meals and drink the liquid afterwards.
Live Action TV:
- Star Trek novel Windows on a Lost World. Captain Kirk, Ensign Chekov and several other crew members are transformed into aliens by a transporter device, including taking on alien personalities. The aliens were carnivorous and ate their prey by injecting them with digestive enzymes and swallowing the resulting liquid like a spider. While in alien form Kirk sucks up and swallows pond algae with his proboscis in a desperate attempt to feed himself. Later on Chekov kills another alien (former human) in self defense and uses his proboscis to suck out its blood.
- This trope is forced upon the beast-men of The Island of Doctor Moreau, most of which had been carnivorous as animals but were forbidden to taste flesh by Moreau, who feared its flavor would make them regress instantly.
- The story Metamorphosis has the main character end up eating garbage after being turned into a human-sized cockroach.
- An episode of Big Wolf on Campus featured Merton falling in love with a vampire and temporarily becoming one himself. The problem is that the vampires in question feed only on werewolf blood, meaning he'd have to eat his best friend to survive. Luckily, he's cured after the vampire who bit him is killed.
- Played for Laughs in Star Trek: The Next Generation. Q gets temporarily turned human (Well, humans would be considered monstrous/animals compared to reality-warping race like the Q) as punishment and at one point learns that he has to eat food to sustain himself. The act of eating alone is a foreign concept alone to the Q. He ends up ordering ten chocoalate sundaes after Data tells him that he's seen chocolate have a positive effect on people that are feeling down.
- The Master from Doctor Who ends up with a voracious appetite for, well, pretty much anything after his ressurection went wrong. He's seen chowing down on burgers, turkey, and even humans due to him being constantly hungry from his life-force draining from him.
- Vampire: The Masquerade. In the supplement An Alien Hunger, several people recently turned into vampires must learn how to acquire blood to drink without alarming the human population.
- In Godzilla: The Series, one of the first monsters ever featured was a giant mutated squid named Crusteacous Rex (or C-Rex for short). C-Rex's diet consisted of tar.
- In addition to the fish-eating habits mentioned above, Zilla Jr. was depicted hunting after mutated rats in one episode. Though, it was more out of territorial instinct than predatory habit.
- Marceline in Adventure Time tends to feed on (apart from blood since she's a vampire) shades of red. No, not that she eats things that are red. She can literally eat the color red. It's implied that all vampires in the series can do this, though it's never explained how or why.
- An episode of Codename: Kids Next Door featured Heinrich being transformed into a blob of sentient chocolate and is able to turn anything in to chocolate. He at first enjoys his power, but soon grows to hate it when he realizes he can eat only chocolate in his monstrous form. Numbah 5 manages to capture him so he can be returned to normal at the end of the episode.