“In my house there's this light switch that doesn't do anything. Every so often I would flick it on and off just to check. Yesterday, I got a call from a woman in Madagascar. She said, 'Cut it out.'”
My college dorm had a hallway light switch that would turn off the hardwired internet access on the two floors below it. eventually, it was replaced by a blank plate.
Switches that control only one side of a duplex outlet are a thing, to control a plugged-in floor lamps for instance, but they confuse the fuck out of people. I've told a few owners of houses about them. The owners had just looked at a ceiling box, couldn't find one, and thought it wasn't connected to anything, a mistake of the architect or electrician. They only ever had something plugged-in in the working outlet and hadn't notified because it just worked. Or, if they used the other one and it was turned off, it must have been broken. It's amazing what people take for granted, even when they've paid a lot of money for a fancy house/condo. My explanation and subsequent demonstration was met with lots of "oh"s and "ah"s.
― Steven Wright