Insanity, Pomegranates, Genius!
Insanely cheery most of the time, does have lapses of sanity and disturbing calm. He likes everyone from the start, even the people who consider him their enemy. He likes fruit, especially pomegranates. He loves to fix things, and he seems to have a massive amount of technical knowledge, since he can make something from just about anything.
A near-infinite amount of items are somehow stored within the baggy folds of the broken straitjacket, but his primary weapon, if needed, is a shotgun. That fires lasers. Big, green, destructive ones. Bwahhh.
I'll let you wonder here because I don't quite know myself, although it's obvious he escaped from a mental institution of some kind.