Two cute incedents... ok, maybe you had to be there... the first was in the early 70's. There was a fellow who used to get some serious munchies every midnight, and he always hit his complex stash of ice creams which nearly filled a freezer compartment. We put a box of frozen peas in there with a radio in it. We ran a trigger wire from the door bulb to the next room where there was a cassette machine and an fm transmitter. George lost it when he heard the box of peas talking to him. He was finally SURE he had too much to smoke...
Another time at a recording studio they had a real metal plate reverb in a "sort of" 'soundproofed' closet. I went in and gaffer taped one of those chirping bird christmas tree ornaments on to the side of the wood crate, and connected it to a timer so it would start about midway through the late-night rock n roll mixing shift. The fun and games went on for nearly a week before the late night mixer finally said something about it, and he thought there was an attic chamber he didn't know about! The rest of us found it WAY funnier than he did, but eventually he appreciated it.
Told you ya had to be there...!