The Heavy - "How You Like Me Now" & Encore

This video is significant for only one reason: talk shows are an exercise in repetition and this completely violates the pattern.

In the almost 30 years the David Letterman has had a show, I don't think he's EVER told the guest to sing it again. As far as I know, this is a phenomenon completely unique to this episode. Although the entire encore performance was not broadcast on television, much of it was. The full thing is available as a web exclusive.