Robin Williams, Adrien Brody, Paul Bettany, and some other dude were all going for the Joker role as well. Maybe Heath had some Brokeback Action with the Casting Director to get the part.
Perhaps they should make a movie out of "The Killing Joke" storyline. It's one of the best Joker stories ever, showing the sick side of this criminal and how he came to be.
They're filming the movie now, and there are some paparazzi pics of Ledger in his Joker getup...somewhat.http://www.superherohype.com/news/topnews.php?id=5530