Paint a bar of soap completely with clear nail polish so it won't suds up.
 707
1  

Take a squirt gun into the rest room stall next to someone and shoot little drops over the wall every couple of seconds while pretending to pee.
 719
0  

Install the Blue Screen of Death screen-saver on someone's computer.
 778
3  

Place a pair of pants and shoes inside the only toilet stall in a rest room to make it appear someone is using it all day.
 702
1  

Fill someone's hair-dryer with baby powder.
 720
1