Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
 601
0  

Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.
 554
0  

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.
 523
0  

Remove the shower head and place a chicken bouillon cube in it, then put the head back on.
 467
1  

Fill someone's hair-dryer with baby powder.
 496
1