Watch Oscar Isaac and Jimmy Fallon Sing a Folk Cover of Katy Perry’s ‘Roar’

The measure of a truly wonderful song? Its ability to still sound great when someone else covers it. Inside Llewyn Davis’s Oscar Isaac gets it, grabbing Katy Perry’s infectious “Roar” and giving it a folk spin. Should Llewyn Davis have just released a cover album? Well, he was friends with Justin Timberlake. (Give us a ten-minute folk version of “Mirrors” and we’ll call it even.)

Watch Oscar Isaac Sing a Folk Cover of ‘Roar’