This year I didn't have time to prepare a proper April fool, but I managed a kind of prank anyway. The toilets where I work have an automatic light switch to save electricity: an infra-red sensor switches on the lights when anyone walks into the gents. And then switches off about 15 minutes later unless it detects any further motion (pun unintended).
All I had to do was adjust the time setting with a screwdriver. So now you go into a stall, sit down and begin a dump, when suddenly the place goes pitch dark. I won't describe the resulting inconvenience in case you're just having your breakfast.
I adjusted the sensor on every floor in the same way. Later on, I was caught in my own trap, but I found that all you have to do is waddle outside the stall to trigger the lights back on. And hope that nobody else comes in at that moment to catch you with your trousers down.
- iPod post