The Joker,recently ranked #2 by IGN's list of greatest villains (fuck you, Magneto),is a cinematic legend from portrals by Jack Nicholson(As Good As It Gets,The Bucket List)and Heath Ledger (Brokeback Mountain,Brokeback Mountain2:Buttfuck Mountain).
The Joker first appeared in Batman #1, making him one of the first Batman villains (except for Prof. Hugo Strange, but you know what - fuck that guy). When the Comics Code Authority deemed him too serious (insert why so serious? meme here), he was changed to a "humorous, cackling nuisance". Now, if he was as much a "nuisance" to Batman as that small abomination you and your significant other have created, running amok in your living room and demanding large quantities of juice, then it was a good thing when writer Steve Englehart returned to his earlier douchebaggery in the story "The Laughing Fish" of Batman#475, despite being one of the gayest named stories in Batman histoy.
Before the dark times (read: Joel Schumacher takes control of the franchise and fufills Miller's prophecy of a "homophobic nightmare"), the Joker was portrayed by Oscar-winning actor Jack " i've slept with over 2000 woman = bullshit" Nicolson, who drew praise for his role, in which he frequently asks people if they've ever danced with the devil in the pale moonlight and attempts to add Kim Basinger to his boning resume. He was then portrayed by Heath Ledger, who was happy to be starring in a mainstream action flick and not Brokeback Mountain 2. Yeah, i know i made a similar joke up there somewhere, but i'm really running out of material and jokes about him OD'ing on prescription meds would still be "too soon".