That reminds me of a video I saw on TV once of two guys playing a piano duet of Jingle Bells, but the guy on the left was using his butt to play a bunch of the bass keys at once instead of playing normally, which acted as the bass track of the song. It was a pretty hilarious effect, and I believe the video is still on YouTube if you search for "Playing Piano with Butt."
Ah, here it is:
Ah, here it is: