I taped a $20 bill underneath one chair. Under all the other chairs was a taped post-it with APRIL FOOLS! on it. At the conclusion of rehearsal I told the kids they had such a great rehearsal that I decided to give a reward that that there was a $20 bill taped under TWO chairs. As expected, the students laughed, and said, "Uh huh...April Fools...nice try Mr. A". I then walked over to the chair of my most obnoxious student, reached under his chair and pulled out the $20. I showed it everyone and said, "Well that was one, but there's one more!" Everyone then immediately turned over their chairs to see the April Fool's note as I walked back to my office laughing.