Jack Napier (Earth-78)

"To them, you're just a freak, like me! They need you right now, but when they don't, they'll cast you out, like a leper! You see, their morals, their code, it's a bad joke. Dropped at the first sign of trouble. They're only as good as the world allows them to be. I'll show you. When the chips are down, these... these civilized people, they'll eat each other. See, I'm not a monster. I'm just ahead of the curve."

- - Joker to Detective Frank Simpson

Jack Napier, commonly known as the Joker, was a homicidal maniac serial killer and former engineer who fell into insanity following the death of his unborn child and his failed attempt of suicide. Deciding that life was sacred, Jack distanced himself from his wife, Jeannie, mutilated himself, including carving a smile into his own mouth, and branded himself as the Joker.