This fear is sometimes unfortunately true. But many movie-turned-musicals have seen unexpected success, usually because of a single actor's portrayal of an extraordinary character.

At least one big hit breezes out every year. Maybe it will happen with the release of Mamma Mia! on Friday, July 18.

In honor of singing and dancing mania, here's the Top Ten Countdown of movie musical characters!

Sing your way through the gallery on the right. Drop a comment if you hit any sour notes!