We were at my house yesterday just doing some quick recording. In one song our singer had to hit a high note and just couldn't get it when the mic was infront of him. On the 4th attempt the drummer comes up behind him and gives him the most solid wedgie I've ever seen. He went WAY past the note he was trying to hit. It was the funniest thing I've ever seen. Another one we always do is pull dwn our pants and moon the guitarist while he's trying to lay down a solo. What other practical jokes do you play on your band while they're trying to record?