If you have friends you will never be short of prank ideas. There might be funny pranks as well as scary pranks but importantly they need to qualify as good pranks. This page gives you an idea of funny April fools prank.
The ketchup prank. Baking soda in ketchup bottle, when shook it will explode. This website has tons of great pranks :)<--- at this point, I think we should engage in a prank war with the other science advisories