Ariana Grande and Kelly Clarkson are going to head-to-head and we're not just talking about on . The pair and their fellow coaches, John Legend and Blake Shelton, are facing off in the premiere episode of Jimmy Fallon's new variety game show, .In teaser from the episode, Fallon tasks Grande and Clarkson with singing a medley of classic hits during the show's «Mixtape Medley Showdown» segment.