In this clip for a documentary series, Heath Ledger's father flips through the pages of the diary that his late son used to prepare for the role of the Joker in The Dark Night. The diary, which says the Joker on it, has a collage of photos: images from Kubrick's A Clockwork Orange, clippings of comics, long hand-written entries, including one about the hospital room scene in which Ledger dressed up as a nurse.
This video is dubbed over in French; there is a rough translation in the description. Ledger's father describes how his son immersed himself in the character, going so far as to locking himself in his hotel for weeks to prepare for the role. The final pages show Ledger in a make-up test for the part of the Joker—and over the test on the final page he's scrawled in huge letters "BYE BYE." His father says simply and heartbreakingly: "It was hard to see this."