While promoting his new film 3:10 to Yuma, actor Christian Bale stated that co-star Russell Crowe would be making a cameo in next year's The Dark Knight.  "Russell's going to actually be in the new Batman movie, which is a big surprise and I want to reveal it to everybody right now," said Bale.

It's unclear what role, if any Crowe would portray in the film.  If Bale was serious about the cameo, it's possible Crowe's role could prepare him to play a villain in a future film.