At the time of his death, Heath Ledger was in the middle of filming The Imaginarium of Dr. Parnassus with director Terry Gilliam. He was playing Tony and the movie was not quite half finished. That left Gilliam with a very large hole to fill and he decided to fill it by casting not one, but three other actors in the role so that when it's all said and done, three different people will play one character - which sounds weird but in a movie about the surreal fight of a man to get out of a deal with the devil, it's not really that crazy.
Anyway, when the movie is released, Tony will be played by Heath Ledger, Johnny Depp, Jude Law and Colin Farrell. And according to this article, Depp, Law and Farrell have now all donated their paychecks from the film to Heath's daughter Matilda. So now Depp, Law and Farrell have a shit ton of goodwill built up with me such that Depp can continue to dress like a hobo, Farrell can continue to look like a crackhead and Law can continue to sleep with the absolute least appropriate women on the planet for a good 5 years and I won't say anything about it.