If you sleep with your head/face toward the mirror then the ghost in the mirror will come out and chop off your head. I heard this from my parents when I was in elementary school and I got my first room. I asked them by the bedframe was facing away from the mirror and not toward it and they told me this story.
This was a ghost story that his parents told him to spook my friend as a child. He mentioned, however, that many of his friends also shared similar stories that were told by their respective parents as a child. The ghost would not always come out from a mirror but maybe spring out from under the bed, from the closet, or a window. It appears that parents use ghosts and scary stories as a means of keeping their children tucked into bed throughout the night, and leaving them to stay still and not clamber around the room.