For the playing in the dirt I one time said "cats scratch in the dirt, are you doing it for the same reason?" Only got a befuddled look, but the other parents thought it funny (except DW)
or "GET THAT PIANO OFF YOUR BACK AND RUN!!!"
Hey quit with the Michael Jackson impersonation and use your glove!" from the old Lewis Grizzard joke from when the Braves were pathetic: "Why are the Braves and Michael Jackson alike? Because they wear one glove for no apparent reason."
One other father and I are trying to find a piano moving company that will sponsor our team. Not sure the girls will get the joke, but it would be funnny