Dailies | ‘Inside Llewyn Davis’ Star Oscar Isaac Performs Katy Perry's ‘Roar’ on Fallon (Video)

Turns out that the pop hit is a pretty catchy folk song, too

Oscar Isaac is singing his way into stardom as the grumpy, yet talented lead in “Inside Llewyn Davis,” and on Monday he sang his way into the hearts of any Katy Perry fans watching “Late Night With Jimmy Fallon.”

When Fallon handed Isaac a guitar and asked him to play something, the actor opted to finger pick his way through Perry's “Roar.”

Also read: How Oscar Isaac's Career Fallback Landed Him ‘Inside Llewyn Davis’

“Llewyn Davis at one point in the movie says, ‘If it was never new, and it never gets old, than it's a folk song,'” Isaac said. “And I think you'd all agree that you can define this song that way.”

“Inside Llewyn Davis” — Joel and Ethan Coen's biggest box-office debut yet — is currently in theaters, and is already earning awards hailing it as the Best Feature of the year.