Remove the shower head and place a chicken bouillon cube in it, then put the head back on.
Change the coffee in the office coffee maker to decaf.
Paint a bar of soap completely with clear nail polish so it won't suds up.
April doesn't fool Chuck Norris, Chuck Norris fools April.
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.
Hide all of the desktop icons on someone's computer and replace the monitor's wallpaper with a screen-shot of their desktop.
Install the Blue Screen of Death screen-saver on someone's computer.
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.
Put a "Please Use Other Door" sign on the entrance to your office building if it only has one entrance.
Fill someone's hair-dryer with baby powder.
Hide an alarm clock in someone's bedroom and set it for 3:00 a.m.