He Implemented The Kubrick Stare
A very big influence for Ledger’s Joker was the character Alex DeLarge (played by Malcolm McDowell) from the film A Clockwork Orange (1971). He mimicked his gestures and what is widely known as the “Kubrick Stare.” A Clockwork Orange is on my current list of films to watch, but after viewing the trailer, wow does it look disturbing.
If Joker was in any capacity close to the craziness of the character McDowell played, then I can’t wait to see all of the inspiration he pulled from Alex DeLarge. I suppose that would fall in line with locking himself up in isolation for a whopping 43 days to study every little nuance of a character.