It's starting to become pretty clear what kind of music gets 66-year-old David Letterman hyped up: high-energy garage rock. We first noticed it when Letterman freaked out over Cage the Elephant's performance of "Come A Little Closer" on the Late Show last year.

Now he's at it again with Chicago rockers The Orwells, who happened to be one of our first Tuesdays Under 21 featured artists. They made their network television debut last night on the Late Show, performing the lively title track of their latest EP, Who Needs You. The high-school aged boys were not short on energy, and lead singer Mario Cuomo (dressed in a Bulls jersey and leopard print socks with mismatched shoes) really seemed to be getting into it. He spent the majority of the song looking possessed (or drunk?), writhing around on the floor and even taking a break on one of the chairs next to Letterman's desk.

Letterman was so impressed by the performance that he demanded an encore and repeatedly chanted, "Come on!" Unfortunately the band wasn't able to play another tune, but Paul Shaffer took the matter into his own hands and began playing "Who Needs You" himself while imitating Cuomo's squirming.

The Orwells are setting out on an extensive tour at the end of the month with the Arctic Monkeys and Twin Peaks. Check out Letterman's reaction to their Late Show performance here, and let us know what you think in the comments section below!