“Ladies and gentlemen… fun.” It’s been eight months since fun.’s “We Are Young” first topped Billboard’s Hot 100, and more than four years since former the Format frontman Nate Ruess started his current band, but hearing a comedian promise us “fun” still provokes a mild dissociative twinge. Luckily, on Saturday Night Live this weekend, host Louis C.K. knew well enough to deliver that line straight, leaving a trench-coated Ruess and a formidable backing band to perform spirited renditions of both Some Nights‘ percussive, AutoTune-happy title track and the theatrical motivational ballad “Carry On,” the latter of which closed with some vocal loops. “I don’t know what I stand for,” Ruess repeated, but his group’s energetic onstage presence gave it away. What’s in a name?