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."