During her Day One headlining set at the 2013 iHeartRadio Music Festival, Katy Perry brought out Juicy J for a performance of "Dark Horse." The track is the latest single off Perry's fourth LP, Prism, due October 18. It's a bit of a departure for the pop singer thanks to the murky Dr. Luke and Max Martin beat. Juicy J does his thing though. "Her love is like a drug/ I was tryna hit it and quit it/ But lil’mama so dope/ I messed around and got addicted," he raps. Watch Perry perform her other Prism track, "Roar," below.