Anne Hathaway had to "physically transform" to play Catwoman in The Dark Knight Rises.

The One Day actress is the latest in a long line of stars including Eartha Kitt and Michelle Pfeiffer to play the formidable character in the forthcoming Christopher Nolan-directed sequel, and she admits it was tough to get into shape to fit into the famous suits she wears.

"I had to physically transform. Chris sat me down at the beginning and said, 'Joseph Gordon-Levitt did all his own fighting in Inception. That one zero-gravity fight. He trained for two months.' I basically left his office and went to the gym and just came out about five minutes ago," she said.

Commenting on the character, who is also known as Selena Kyle, Chris claims she represents an "underlying" sense of darkness in the film, which is the last he will direct. "She has a very strong way of protecting herself and those she cares about, which implies an underlying darkness," he told Entertainment Weekly.