There was quite a few there. I'm sure everyone has heard of the filling holes in walls one, and I have tried it, just make sure the house isn't yours.
When I was a kid I had a new watch with a glass face, and I cleaned it with a harsh chemical when it was dirty which caused it to haze the glass so much you couldn't read it. My dad felt bad, and the next day picked it up just looking at it and rubbed it with his thumb. He aparently still had a bit of toothpaste on it from brushing, and it made a clean spot. He then took it upstairs and cleaned it with toothpaste, and it looked good as new, so I definately believe the shower door thing. Go figure.