Watching Mirrormask, a few days after seeing the Mary Poppins trailer with the horror motif, and coincidentally the Bewitched ramake last week, reminded me that there seem to be quite a few films and TV shows with the "mirror image comes to life" effect - it's an obvious one for the special effects people, and of course it hits on a psychological / mythical level. The most obvious ones that come to mind are
Alice Through the Looking Glass
Bewitched (the uncle appears in the mirror)
Harry Potter & Philosophers Stone
Angel (the real Cordy meets her replacement)
Now I want to write something on this theme, not quite sure what at this stage. Maybe fanfic, maybe game related - there was something vaguely like this in the Forgotten Futures / Flatland crossover I ran at Dragonmeet, I may make the interface between game worlds a mirror instead of a drawing as at present.