was intended to portray Batman from the criminals' point of view. The improved Batsuit design let him show more of Bale's Keysi-fighting method training. Christopher was aware Nicholson's popular portrayal of the Joker would invite comparisons to his version, and wanted an actor who could cope with the associated scrutiny. Ledger's casting in August 2006 was criticized by some industry professionals and members of the public who considered him inappropriate for the role; executive producer Charles Roven said Ledger was the only person seriously considered, and that Batman Begins positive reception would help alleviate any concerns. Christopher was confident in the casting because discussions between himself and Ledger had demonstrated they shared similar ideas regarding the Joker's portrayal. Ledger said he had some trepidation in succeeding Nicholson in the role but that the challenge excited him. He described his interpretation as a "psychopathic, mass-murdering, schizophrenic clown with zero empathy", and avoided humanizing him. He was influenced by Alex from the crime film A Clockwork Orange (1971), and British musicians Johnny Rotten and Sid Vicious. Ledger spent about a month secluding himself in a hotel room while reading relevant comic books. He developed the character's voice by mixing a high-pitch and low-pitch, which was inspired by ventriloquist performances. His fighting style was designed to appear improvised and erratic. Ledger spent a further four months creating a "Joker diary" containing images and elements he believed would resonate with his character, such as finding the disease AIDS humorous. Describing his performance, Ledger said: "It's the most fun I've had with a character and probably will ever have... It was an exhausting process. At the end of the day, I couldn't move. I couldn't talk. I was absolutely wrecked." In a November 2007 interview, Ledger said when committing himself to any role, he had difficulty sleeping because he could not relax his mind, and often slept only two hours a night during filming. Christopher wanted to cast an actor with an all-American "heroic presence" for Harvey Dent, something he likened to Robert Redford but with an undercurrent of anger or darkness. Josh Lucas, Ryan Phillippe, and Mark Ruffalo were considered, as well as Matt Damon, who could not commit due to scheduling conflicts. According to Christopher, Eckhart had the all-American charm and "aura ... of a good man pushed too far". Eckhart found portraying conflicted characters to be interesting; he said the difference between