A "nip-sync" battle.
Fallon and the Brooklyn Nine-Nine star "duetted" on the Paul McCartney and Stevie Wonder song "Ebony and Ivory," with Fallon receiving a computer-generated assist from some very buff Tonight Show staffer (with a prominent shoulder tattoo).
Crews, who will start hosting Who Wants to Be a Millionaire? this fall, will also be appearing in the new Adam Sandler and Drew Barrymore rom-com Blended, opening this weekend.
Have no fear, his pecs will be on display there, too.