1. Sugar and spice (or is it salt?)
A classic April Fool's prank is to swap out the sugar and the salt. That means putting sugar in the salt shaker, and adding salt to people's coffee. Assuming your friends and coworkers aren't too serious about their coffee, it should be a pretty fun prank.
2. Balloons galore!
Fill someone's room with balloons of every color! The clean up might take a little bit, but who doesn't love balloons anyway? Just remember to check if they have a latex allergy first.
3. Soap with no suds
This one is easy! Take a bar of soap and coat it with some clear nail polish, and voila! It's soap that can never get soapy. Hand it to a friend and watch them struggle.
4. Push or pull?
A daily struggle one goes through everyday: is this door a push or pull? Trick your friends and coworkers by putting a sign up that advertises the wrong action. Soon they'll be questioning everything: up or down? Left or right? What is what?
5. Don't scream...
Buy a bag of fake insects: roaches, spiders, grasshoppers, the works. Then, hide them in various drawers, couch cushions or even tape them to the inside of a lamp shade. At some point during the day you're likely to hear an earth-shattering scream, and then hopefully some laughter.
