"Everything about what he does from every gesture, every little facial tick, everything he’s doing with his voice – it all speaks to the heart of this character. It all speaks to this idea of a character who’s devoted to a concept of pure anarchy and chaos. It’s hard to get a handle on how those elements combine. The physicality reminds me of the great silent comedians. It has a bit of [Buster] Keaton and [Charlie] Chaplin about it.
The voice is very difficult to imitate. Every film set, on every crew there are dozens of talented mimics who are always taking off different performances or lines that they’ve heard from actors before, but no one could do The Joker. No one has been able to imitate it successfully. It’s very elusive and complicated, but working with Heath you would see that he very precisely worked out every aspect of him. “
—Christopher Nolan talking about Heath Ledger’s Joker