Calling all Sharks, Jets, Pinball Wizards and Wicked Witches. What good is sitting alone in your room, when you can be singin’ in the rain about your favorite movie musicals? With Mamma Mia 2 Waterlooing its way to big screens soon, this week’s Showdown celebrates the very best celluloid musicals. There’s nothing like a song and dance number to really get across the clear and present danger of Nazis approaching your happy mountain hideaway. List your top ten, and make ’em laugh down on Sing Street, ’cos Grease is the word.