Cardboard and paper cups

by Habibah
(USA)

When the person is in his/her room taking a nap or doing something, take paper cups and place enough on the floor to cover the width of the door, and fill the cups with water. Then, place a long thin piece of cardboard and place it on top of the cups. Then put cups on top of the cardboard and fill those cups with water. Repeat this process until the cups and cardboard cover half of the door. Now, call the person out of the room and they will be in for a surprise.(If the cups or cardboard keep falling tape the cardboard to the wall or door but not to tight or else they will keep the cups and water from falling.