One of the toilets in my house seemed to be haunted.
Once in a while, sometimes several times in a week and other times not for a month or two, it would flush itself when nobody had been near it.
The other day I talked to a plumber and learned the problem was called "ghost flushing." It happens to other toilets and apparently I'm not the only one who thinks it seems spooky.
What actually happens is a tiny bit of water leaks out of the tank over a period of hours or days until the water level gets low enough so the mechanism opens and allows new water to refill the tank.
That's what causes the flushing sound.
Okay, the mystery is solved.
However, as a writer, I like the original concept better. I can think of all sorts of story possibilities about a haunted toilet.