cool prank

first buy around 100 cups.Fill them all upwith water. Stack them up infront of your friends door that he usually walks in from. (hint hint make sure that you yourself can get out of the room). For more intertainment fill the whole floor with the cups of water so he has to pick them all up. For grand intertainment take a trash can that doesnt have holes and fill it with water. Lean against the door of your choice (make sure that your frined has to pull open the door, not push the door) and so when he opens the door it falls into his room.