For the first time Heath Ledger's father Kim allowed the public to see his late son's journal on Thursday which offers a glimpse of the Australian actor's dedication to the Joker role in Batman's sequel The Dark Knight.
A short clip was released May 30, which showed Heath's journal entries where he noted traits and qualities he wanted the Joker to have.
Part of a German documentary called Too Young To Die, the older Australian man revealed his son's preparation for the role.
The film clip starts with Kim opening the red and blue bound book and showing the hand-written notes, drawings and photographs of clowns and pages of comic books.
"This is the diary," Kim said in the clip.
View footage of Ledger's Joker diary from Too Young to Die below.
The diary, placed next to the actor's Best Supporting Actor Oscar, which he won posthumously for the role, shows that Heath drew inspiration from Malcolm McDowell's character in Clockwork Orange and even from hyenas.
Kim said his son "immersed himself in the upcoming character on every level level."
It Heath's typical approach to playing characters, Kim explained.
"He liked to dive into his characters but this time he really took it up a notch," Kim added.
Heath was 28-years old when he was found unresponsive in his New York City apartment in January 2008. While Heath's death was ruled accidental the diary reveals he was struggling with the role and his own emotions.
The Dark Knight was released nearly six months after Heath's death.
Before his death Heath said in an interview with Empire Magazine that he "feared" the role but wanted to make it different.
"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," Heath said.
"I ended up landing more in the realm of a psychopath...He's just an absolute sociopath, a cold-blooded, mass-murdering clown, and Chris has given me free rein. Which is fun, because there are no real boundaries to what The Joker would say or do. Nothing intimidates him, and everything is a big joke," Heath added.
Heath left behind his daughter, Matilda Rose, who he fathered with actress Michelle Williams.