A lot of the humour comes from Granny Klump and her gigantic sagging bosom. Why do people find that so funny?

Well (laughs), first of all the hanging weight; then if you've never seen an old woman jumping around with her titties flapping, it's funny.

Which character did you find most amusing to play?

I don't have any, the process is kind of the same for me. I've got to sit in a make-up chair and go talk to a tennis ball no matter what I'm doing. I look at it as being the same performance. But I like the sweetness between the mother and the father; it's like an outrageous comedy but you have his really sweet scene between the parents. I like that kind of stuff.

Eddie Murphy on the challenges of playing more than one character in a film.