Many parents who bring their children with autism to my clinic complain that their children are fascinated--really happily obsessed with mirrors. They tell me that their child will spend countless hours watching themselves in mirrors---posing--performing different movements over and over again. Not all children with autism are interested in mirrors but a significant number are. Some parents take all of the mirrors down and then find their child looking at their reflections in glass windows or doors. In my case history eBook, Little Bubba would look at his reflection in the toilet bowl water.
No one knows what causes this obsession and no one has a good procedure to treat it that I know of besides taking all of the mirrors down or redirection the child to some other activity.