WARNING: Some people may consider the following SPOILERS. It may be just too much for some of you sweet little princesses out there. If you are a sweet little princess, GO NO FURTHER.
GARY OLDMAN - You know what, I think that all along with this [director] Chris [Nolan] has tried to root the thing in some reality, and you know where the franchise ended up, and so he wanted to make it more realistic given the framework that it's "Batman." He wanted it to be more realistic and darker and edgier rather like the comic book, and so the inspiration for the Joker is punk, which explains the colored clothes and so it is very sort of Johnny Rotten, very punk. The smile and the scars from a razor and he's got like a sort of rinse, a green rinse that remains there in his hair, and so you look at him and he’s very forbidding and not like a clown. It's very dangerous, very unhinged. It’s like Coco the Clown on crack.
Head on over to Wizard to get the whole interview. Click on the source link below.