I used to have a piano teacher who accused me of going through her house when I was waiting for my lesson. I'm still not sure what the hell she was talking about, because I never went further than the route we were supposed to take...coming in the back door after school, going down the basement stairs, and waiting in the little area outside the lesson room. But she said I was up going through drawers and stuff. I suspect there are more crazy-old-lady piano teachers out there than we think.
In the eighties I had a piano teacher who dated the guy who was the stand-in for Darth Vader in the Star Wars movies. At least, that's what he told her, and that's what she told everyone else, just about every hour on the hour. It was her big claim to fame. She was crazy enough, but probably only about 35.