The MSU hockey team had already been eliminated earlier in the day, but the MSU fight song was still proudly being played in one hockey rink — one where MSU wasn't even playing.
Late in regulation with their team leading Michigan 2-1, the Cornell pep band played the MSU fight song, bringing in a new level of how to troll an opponent. This had to be planned. The band would have had to bring sheet music for the MSU fight song or something, because I assume it's not part of their normal playlist. (Update: This appears to be something Cornell has done before, playing an opponent's rival's fight song).
If you look at Shawn Hunwick's face in this video, I wonder if he recognized the tune. U-M actually tied the game up a few minutes after the song was played, but Cornell won in overtime.