When Christian Bale and Liam Neeson were fighting on the frozen lake they could hear the ice cracking beneath their feet. The next day, the lake was completely melted.
The first four days of scheduled shooting resulted in no film being rolled. Instead, Christopher Nolan screened two films for the cast and crew with a break in between. The eight films were (in order): Heat, Cat People, Citizen Kane, King Kong,Batman Begins, Black Sunday, A Clockwork Orange, and Stalag 17.
The Joker’s face paint was reportedly designed by Heath Ledger himself, who used white clown makeup and cosmetics from a drugstore. Once his design was approved, the makeup team was responsible for replicating the look each day for filming.
While the movie was filming a chase scene on Lake Street, the Chicago Police Department received several calls from concerned citizens stating that the police were involved in a vehicle pursuit with a dark vehicle of unknown make or model.
To block the three-way sex scene with two prostitutes, Mary Harron and Christian Bale watched x-rated tapes. In her commentary, Harron says Bale made stick-figure drawings of the positions he thought would work best.