"Especially fun for the married guys."
Some fellows in my guard unit used to put ladies underwear in their buddies dufflebag at the end of summer camp. They prefered very large sizes. One learned to always check one's duffle before taking it home.
"at the airport..."
Reminds me of another one my friend Frank pulled. Back in the 60s, Five Day Deodorant Pads were popular. Frank's roomate started using Franks and then puting the pads back in the little jar they came in. Frank bought an extra jar. Frank was taking a chemistry class. About five days later all the hair fell out of his room-mate's arm pits. It did cure his room-mates persperation problem though.
"Gay pride stickers".
A found a book one day entitled fifty ways to get even with your ex. One was to print up a bunch of flyers for some thing like the local chapter of the "Gay and Lesbian League of Communist Supporters" announcing this months meeting and include your ex's phone number. The book suggested puting these flyers under windshield wipers at your local mall and the local chapter of the VFW.
"Once upon a time" a big aerospace firm was going to show a DVD about a missile system to us around lunchtime. The projector and everything was set up for a few hundred people to watch. Lunchtime came and went. Those that talk contracts and the big engineers came back late. Then everybody got called back to watch a movie about a defense system. Lights out-movie on. A dirty movie started playing! It took a while to turn the lights on to turn off this projector. The original DVD was swapped and in the dirty movie box UNDERNEATH the projector stand.
I kept my mouth shut about this one. We got the contract:)