HOLLYWOOD: Kristen Bell wore her pyjamas to work "on principle" when she was recording her voiceover for Astro Boy.

The actress made the confession at the movie's premiere in Hollywood.

"Very literally I would show up in my pyjamas, even if I had to record at three or four in the afternoon I would change back into my pyjamas just on principle because if you have a job you can show up to on pyjamas I say go for it," she confessed.

"It's wonderfully comfortable," she added.

The Couples Retreat actress admitted that at times she felt a little crazy recording her lines.

"It was a little bit strange to be in a recording booth with no one else. Having to converse with someone that's not there is pretty frustrating

"The hardest thing was doing the action sequences because you're pretty much standing in a room by yourself karate chopping a wall, going 'hwah', 'hwah'," she said.

As for having a superpower like Astro Boy, Kristen joked there was no competition, saying: "I would have the machine guns coming out of my b**t because I just feel like someday that's going to be necessary!"