The Joker is a supernatural being. Take away his permanent white skin and he's just a crazy man with some face paint. But, his white skin and his sadistic personality makes him the Devil of all comic books. You can't kill the Joker, you can't hurt the Joker, and you're gonna have a hell of a time trying to stop the Joker.
Very well said.
Of course, Nolan doesn't read the comics so he didn't grow up with the character the way most of us have so therefore he doesn't give a ****.
The conversation between him and somebody at WB who knows about the comics (maybe Goyer?) probably went something like this:
Knowledgeable Person: Hey, Chris, you know fans are expecting you to give them the Joker in the sequel after that little tease you gave them at the end of
Begins.
Nolan: Yes I know. But can I please have another vest?
K.P.: Um...yeah, sure. We'll get to that. But uh, back to the sequel. Who were you thinking of having as the villain?
Nolan: I don't know, what are my options? Aside from having a new vest, of course.
K.P.: Well the studio is really pushing for the Joker.
Nolan: What's his story then?
K.P.: Well he's a married father with a background in chemistry who tries to make ends meet as a comedian but can't so he turns to crime, and in one of his heists at a chemical plant - during which he learns that his wife and child have been killed - The Batman unintentionally knocks him into a vat of chemicals that make his skin pale, his lips red, and his hair green.
Nolan: Wait...Batman creates him by knocking him into a vat of chemicals?
K.P.: Yes, actually it's one of the most well-known and adored villain origins of all time, Alan Moore --
Nolan: Horse ****.
K.P.: Wait, what?
Nolan: Horse ****. We'll have him be a bank robber who likes dressing up as a clown.
K.P.: But --
Nolan: Now where's my goddamned vest?