The Dark Knight is widely considered one of the greatest comic book movies ever and regularly ranks toward the top in fan polls about the greatest movies, period. Part of the reverence for the film revolves around the legendary performance of Heath Ledger, who passed away before the release of the film that earned him an Oscar. It's well known that Ledger's commitment to the iconic role was complete down to the way he famously kept a Joker diary while developing the character in isolation. Today, we look through the history of his performance, and investigate ten things that most fans don't know about his role in the movie.

Heath Ledger was the only actor offered the role.

The arrival of Gotham's Clown Prince of Crime was teased at the end of Batman Begins, Christopher Nolan's well-received reboot of the Caped Crusader. Several actors pursued the role. Adrien Brody...