There is quite a bit of setup to make this work right, but it is really funny. Place a couple of tables or card tables beside each other (leaving 8 inches between them) and cover with table cloths that hang down to the floor. Overlap the table clothes together leaving just enough space for someone’s head to come up between the two tables. Place four boxes on the table and ask one person to kneel on the ground between the two tables (now slightly spread apart) with their head above table level under one box. Put different kinds of balls under the other three boxes.
Do all students do not see. Now choose three volunteers and have them leave the room. Call the first contestant in and tell them that they are being timed to see how quickly they can lift up each box and say what kind of ball is under it. It works best if the person is the last one they come to. When they lift the box off the person’s head he or she yells. It’s fun to watch the reactions of the whole group and the contestant. Do this for every person up to the last contestant. For the last contestant, give them the same instructions. As you are talking (making everything sound the same) be handing the contestant a whip cream pie. When the box with the person under it is lifted, he screams, expecting to scare the person just as he has the previous persons–but SURPRISE! He gets creamed by the pie!