Director Tim Burton has found the ultimate test of Hollywood superstar Johnny Depp's talents - a movie ballet. The pair have worked together in six movies to date, including Edward Scissorhands, Sleepy Hollow, the forthcoming Sweeney Todd - and Burton has yet to found a skill Depp can't pick up. He says, "Singing could be his limit. Dancing I'm not sure about. I've asked him to do a ballet next and he's not sure about that one."