This year's NFL Draft is taking place in Las Vegas, which means there have been far more celebrity appearances than normal on the broadcast over the course of the last few days. Viewership and interest in the event drops heavily on Day 3, which means it can get weird.
It sure did this year as the Blue Man Group made a rather unexpected appearance on NFL Network aside Rich Eisen during the final rounds of the draft.
I do not know why this happened but the better question is why not? The fourth through seventh rounds can be boring and the Blue Man Group is, if anything, entertaining.
Highly recommend going to see them if you have a chance. Very unique and a remarkable visual experience.