We all flash plumber's crack or even worse, ass crack, sometimes. But if you're a celeb, the photogs are hiding in the bushes waiting for you to pick that wedgie. You may think you know everything about your favorite celebrity's butt—but can you identify them by their crack flash? Find out with our name-that-celebrity butt crack quiz. Starting with the tush above ... is it Christina Ricci? Kristen Stewart? Or Katy Perry? Keep clicking to find out...