One from a friend of long ago, which I swear I'll repeat myself sometime: You have to be eating in a restaurant with common glass "shakers" with tin screw-on caps. Take the caps off. put a scrap of paper napkin on the top of each shaker. Fill one cap with salt, one with pepper. Put them back on the wrong shakers.

The head of our quality inspection department walked in one day, put a banana on his desk, and left. I had a banana in my own lunch that day. I quickly ate my own, left the peel on his desk, and hid his banana. I don't think he knew whether to get mad or just crack up. He immediately assumed the culprit was another crew member who had the biggest reputation for pulling crazy stuff.