I'm going to repeat a couple of good prank stories that I know happened.

Man heard that another man was hitting on every woman in the community, including his wife, so he goes and buys a real sexy pair of panties, jacks off on them, and then puts them in the guys car, with the following note......Here's something to remember me by, with your cum still on them. Guy's wife finds them first and the chit hit the fan. No, I wasn't involved, but I know who was, and I always figured the guy had a good reason for doing what he did.

Back in high school a friend of mine was always taking a box of Chiklets, after it was empty, and filling it up with Feenimint, which looked exactly like a Chiklet. He'd pass them out to other people. Feeniment was a laxative, and he pulled that stunt more than once.