He is a horrible creature and no one knows how he came to be. Some say he was formed in the sewers, others say he was the result of a mystic spell that back-fired, or perhaps science gone horribly horribly awry but regardless of how he was created, he's 100% excrement and he was made from the feces of the 666 evilest people who ever lived. There's a little Hitler, a touch of Ed Gein, and a half pound of Jeffrey Dahmer. And thats a lot of evil shit. Shithead works as Mr. Rictus's main goon.
During Mister Rictus's takeover, Shithead killed The Professor and then tried to go after Fox and The Killer. The Killer used some bleach to weaken him and flushed him down the toilet.
Shithead is based on DC Comics' Clayface, a humanoid monster with a malleable body made out of mud.