One night I was asleep in my basement. I awoke in the middle of the night and I noticed in the upper corner of the room there was a focused spot of white light behind one of my pins.
I live in an old house, so I figured there was a new crack in the foundation letting light in from outside so I didn't think much of it.
The next day I was ready to seal the crack, but upon investigation there was no crack and no gap between the basement cinder blocks and the frame of the house. Light coming in from a window could not have made the angle to shine in the corner like that.
There may be a perfectly normal explanation for the light, but I never found anything that would cause it. Nobody but me was in the basement that day or the next day and I didn't add or move anything in the room. I've never seen the light appear since.
Not much of a story, but things like that get your mind thinking.