I swear I read somewhere that he was studying killers and trying to tap into the mind of the criminally insane, so he can play Joker.
“He was having fun. He wasn’t depressed about the Joker,” his sister said. However, the lengths to which he went to play the character have been well documented.
Ledger said in a New York Times interview that playing the Joker was ‘physically and mentally draining’. It also affected his already troubled sleep, with the actor saying that he could manage just around two hours of sleep on certain days.
Ledger famously locked himself away in a hotel room and maintained a diary to prepare for the role. He told Empire in a 2007 interview, “It’s a combination of reading all the comic books I could that were relevant to the script and then just closing my eyes and meditating on it. I sat around in a hotel room in London for about a month, locked myself away, formed a little diary and experimented with voices — it was important to try to find a somewhat iconic voice and laugh. I ended up landing more in the realm of a psychopath — someone with very little to no conscience towards his acts. He’s just an absolute sociopath, a cold-blooded, mass-murdering clown.”
A documentary featuring Ledger’s father, Kim, shed some light on the notes the actor made in his diary. Glimpses of the little journal showed images of hyenas, pictures of the character Alex DeLarge from the film A Clockwork Orange, and also handwritten dialogue. The final page of the diary had the words ‘bye bye’ written in large letters. “It was hard to read that,” Kim Ledger said in the documentary. “He galvanized the upcoming character. That was typical of Heath. He would do that. He liked to dive into his characters, but this time he really took it up a notch,” Ledger’s father added.