The Boogeyman, usually just called Boogey is a recurring villain in the show. He is the main antagonist in Billy & Mandy's Big Boogey Adventure as well as the true antagonist in Wrath of the Spider Queen(though he only appeared in flashbacks) and as spin-off in The Boogeyman Show. As his name implies, he is a professional Bogeyman. He also has his very own crew and pirate ship, Boogey Bay, as well as a law degree. He lives in an apartment in the Underworld.
Boogey has mint green skin, purple eyes and is hairless, although he is always seen wearing a hat of some kind. He has large, pointy ears, long curved nose, and sharp teeth. His fingernails are long and dirty. He is just as tall as Grim, and stands out with his unique sense of fashion. Casually he is barefoot and wears a blue nightshirt and a red fez. Sometimes, he wears a pair of glasses.
Boogeyman has the role of the stereotypical bully down cold. He is a snake in the grass, conceited, ruthless, crass and intolerably full of himself. He has a life-long history of tormenting people by bullying, pulling nasty pranks (in particular), extortion and childish name-calling. His pet punching bag is Grim, who, still in adulthood, falls for the childhood bully's old tricks.
But even with all the imaginable qualities of a "Class A Twerp", Boogey finds it impossible to scare modern day children with the exception of sissies and Irwin. He is very self-conscious about that and blames it on, in his words, "cartoons, and video games and the tuba". The only thing he is really good at is being a pain. His old middle school yearbook crowned him as "Biggest Jerk".
Boogeyman can shapeshift, make people hallucinate and trap them in endless nightmares. (He calls this "Scareology") He is also able to inhabit objects, and this is probably how he moves around in strangers' homes unseen.
Boogey's first appearance was "Bully Boogie" where he returned to ask Grim for a final scare-off, which Grim won. Boogey was banished to the nightmare realm, but reprised his role as the primary antagonist in Billy and Mandy's Big Boogey Adventure to prosecute (and get revenge) on Grim and his friends.
He won the trial and was granted custody over them, offering to send them as far away as possible. His real plan, however, was to sail to the Isle of Peril to find Horror's Hand and try to convince Mandy to become his friend, so she would protect him. He punishes her rejection by cursing her with a sleep spell, which is eventually broken by Irwin, who uses the oppurtnity to kiss Mandy to wake her. All characters continue trying to find horror's hand.
Upon finding The Hand, he's confronted by his worst fear: not being scary. He suffers from a series of accidents, which results in him getting amnesia and now being afraid of everyone and everything, and secludes himself in his home. Grim reveals that the hand was turned off, so the hand did not actually make Boogey see anything.
He last starred as the true antagonist in Wrath of the Spider Queen, as a middle school student, in a series of flashbacks depicting him being cocooned by Velma Green, stung and put up on a flagpole and humiliated, sabotaging the selection for a new Reaper, as well as destroying Grim and Velma's friendship. He did not succeed because of cheating, and Grim threw him into a crack by parting the auditorium's floor in front of everybody, making a lasting impression that eventually won Grim the election.