The Boogeyman (The Grim Adventures of Billy & Mandy)

An old arch-enemy of Grim's since middle school, and a former school bully, Boogey played pranks on Grim throughout his school career. Boogey is, in fact, the Boogeyman himself, and can shapeshift in order to scare people. Unfortunately, though, he is completely unable to scare kids because they have become desensitized by modern media.