Fanon, short for fan-canon, is a term referring to a depiction of a character in a fan's work that, while not necessarily canon, catches on with the fanfiction community well enough that it gets included in other people's stories.

Fanon is, by definition, not canon. It does not have to be universally agreed on among fanfiction authors either, only portrayed with moderate frequency in unrelated works.

An example of Bully fanon is Trent Northwick, who is regularly described as a lech towards new girls at the school and having horrible tobacco mouth.