Big Eater/Fan Works

John in With Strings Attached. Eats at least three times what a normal person eats. He can ingest and draw nutrients from just about any organic substance. As a side effect, he's immune to poison and drugs, including alcohol.
Socrates from Calvin and Hobbes: The Series; at one point he builds and tries to eat an actual food pyramid.
In The Tainted Grimoire, many are they who are shocked at how much Cid and Ensei can eat.

In A Very Potter Musical, Ron Weasley always has a snack, including but not limited to: a carton of Chinese food, a bag of Funions, Twizzlers handed to him by a member of the band, and a Hershey bar the size of his torso.

Ron: Accio double-stuffed!

Wheatley becomes this after GLaDOS implants his brain into a human body in the Portal 2 fic Test of Humanity. He ends up eating everything in Chell's fridge after tasting food for the first time, and, later on, G La DOS tricks him into eating 30 cakes. By the end of the fic, he's grown noticeably fatter.
- The sequel has Chell's roomates being unable to make anything for dinner because Wheatley already ate nearly everything. And, Wheatley then admits he made a large order for Chinese takeout...most of it being for him to eat.
Sheila Brainstorm and her mother from Calvin and Hobbes: The Series - the latter ate an entire turkey in a few bites.