"Candid Camera" had some fun when they hooked up the misters at the produce case to a motion sensor; customer leans over to check the lettuce, and the mister sprayed them! [Linked Image]

At one job we had a "stupidvisor" who did not approve of radios. Not a problem; the radio in my work area was tied into a relay, along with a sensor from the production line. Anyone coming near the area would shut down the radio- both before they could hear it, and giving us advance warning.

Probably the best "joke" was completely unintended. In the name of energy conservation, the customer (who had earlier eschewed individual switches for each room) wanted all the lights on a motion sensor. Add to that a new furniture allowance- and as soon as someone went into their cubicle they became invisible. They could not understand why the lights kept "flickering."