Cover the TV remote sensor with a piece of tape
Laugh as your TV obsessed friend tries to figure out why the TV won't work!
Super glue a few coins to the ground in a popular area
Watch as hilarity ensues.
Put a WARNING sign on a random door
WARNING: Rabid Squirrels Inside
Print out a scary photo and hide it in people's desks
Swap the mens and women's bathroom signs
Bring clothes in your backpack and change every 30 minutes