Manchester, England-based quartet WU LYF are getting ready to take over after making a pretty huge impact in 2011 with their acclaimed debut, Go Tell Fire to the Mountain. And it was last night that the guys left their biggest mainstream impression yet. They made their TV debut with a spirited performance of "Heavy Pop" on The Late Show With David Letterman that you can watch in the above video. The best part? Letterman cracking up at the end and just barely getting out an "Oh my." We concur.