Heath Ledger’s Dad Shares Diary Actor Wrote While Filming “The Dark Knight”

Heath Ledger put his heart and soul into playing the Joker in "The Dark Knight."

In order to fully understand the character he was portraying, the late actor kept a diary written from his character's point of view throughout filming. In a new documentary series called "Too Young To Die," Heath's father, Kim, shows viewers inside that diary, which sits on a table next to his son's posthumous Academy Award he won for that role.

"This is the Joker's diary. In order to inhabit his character, he locked himself up in a hotel room for weeks," Heath's father explains. "He would do that. He liked to dive into his characters, but this time he really took it up a notch."

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Kim also points out a page showing "The Dark Knight's" hospital scene where the Joker dresses up as a nurse. "The hospital scene is interesting because when he was a kid, his sister Kate liked to dress him up as a nurse," he says. "He was really funny like that. He also was [funny] in the movie."

"Before the end of the shooting he wrote 'bye bye' on the back of the page," his father says. "It was hard to see this."

"The Dark Knight" hit theaters six months after Heath's tragic death in January 2008.