Crowning Moment of Funny: Pratically every single one of his interviews. You don't need to watch a lot of them to understand why the Potter fandom considers him the biggest troll of the whole cast, which is saying something.
Draco in Leather Pants: Almost the Trope Namer. Many people, including J. K. Rowling herself, attribute the phenomenon to Felton's attractiveness, but he can't be completely responsible as the fandom had decided Draco was hot before anyone had seen a single frame of the first movie. In fact, the trope name comes from a scene in The Draco Trilogy, the first two installments of which predate the films. However, Felton's casting certainly contributed to the character's popularity among preteen and teenage girls.