David Letterman may not be young, but Fun. are — and they celebrated it by performing their inescapable hit on ‘The Late Show’ last night.

The New Yorkers, whose ‘We Are Young’ was just nudged out of the No. 1 spot on the singles chart by Gotye, hit the stage and proved they’re not just a radio band — they sounds great live, too.

The piano is more audible in the live version of the track, as is the slight breathiness of frontman Nathan Ruess’ vocals (a trait that actually works in his favor and gives his voice character and distinction). The only downsides to the live performance? The lack of Janelle Monae, whose soft voice adds a beautiful quality to the bridge of the song, and the weird stuff Ruess kept doing with his tongue. Seriously dude, keep that in check. It’s awkward.

The band clearly had fun performing — in the beginning of the song, Ruess looked wide eyed, as if he couldn’t believe how lucky he was to be on the show. Letterman summed it up well: “Nothing but fun!”

Watch Fun. Perform ‘We Are Young’ on ‘The Late Show With David Letterman’