A diary Heath Ledger kept during the filming of “The Dark Knight” surfaced, adding some insight to Ledger's state of mind during the filming of his (posthumous) Oscar-winning performance.
Ledger's father, Kim, shows the eerie journal in “Too Young To Die,” a German documentary about the late actor.
In the clip above, he talks about the lengths his son went through to get ready for any character he was set to play. Kim said,
He pretty well locked himself up in a hotel in his apartment for a month or so to sort of galvanize the upcoming character in his own mind. That was typical of Heath on any movie. He would certainly immerse himself in the upcoming character. I think this was just a whole new level.
In the diary, you can see a photo of a hyena, stills from “A Clockwork Orange,” panels from comic books featuring the Joker and notes Ledger wrote down.
Kim mentions how one of the entries titled “Hospital Room” was seemingly inspired by how Heath's sister Kate would dress him up as a nurse occasionally.
Heath Ledger died in New York in 2008. A few months later, he won the Oscar for Best Supporting Actor for his role as the Joker in “The Dark Knight.”