'The Flash' & 'Supergirl' Musical Crossover Trailer: Sing for Your Life

Even if you're not a CW superhero-show maniac, you must be wondering how the hell The Flash and Supergirl are going to pull off a musical episode. (Plot-wise, anyway; Grant Gustin and Melissa Benoist were both on Glee, so.)

Now a teaser for the March 21 episode shows fellow Glee alum Darren Criss as the villainous Music Meister. He announces that the Flash and Supergirl will find themselves transported to a movie-musical world—without their powers. "Reach the end of the plot, you get to go home," he says. "Although I should mention, if you die in here, you die out there."