“Sometimes… sometimes I think the Asylum is a head. We’re inside a
huge head that dreams us all into being. Perhaps it’s your head, Batman.
Arkham is a looking glass… and we are you.”
- Arkham Asylum: A Serious House on Serious Earth
He’s the hero Gotham deserves, but not the one it needs right now. So we’ll hunt him. Because he can take it. Because he’s not our hero. He’s a silent guardian. A watchful protector. A Dark Knight. — The Dark Knight (2008) dir. Christopher Nolan
“A doctor at Arkham once described for me The Joker’s state of mind: imagine trying to solve the world’s most difficult math equation while you’re surrounded by six televisions that sit five inches from your face–all tuned to different stations, all rapidly switching channels, all with the volume at full blast. That’s what it’s like to be The Joker.” - Batman: Cacophony
Heath is one of those actors who, in his best work, completely
transforms himself and that sort of consumes his star quality. He’s
creating something that’s entirely original for himself and so he’s
never done anything like this before. I can’t say that I was hugely
surprised or worried about the reaction because whoever we would’ve
cast, it’s going to be tough for people to know how the palette is going
to work. Particularly with Heath, who’s dredging something up from a
side of himself that you’ve never seen before.
— Christopher Nolan on Heath Ledger as the Joker in The Dark Knight (2008)