I actually forgot about the whole rock band being in the movie...until today. I was watching the movie today with my friend, and when it started playing that part, I literally said, "Whoah, what the fudge is up with that?" It was a formal ball, not a teenage rock concert! All they were missing was Maggie Smith rocking out (without her hair in a bun!), Michael Gambon break dancing, and Alan Rickman doing the worm.