I was discussing Contact and the mirror trick shot in it with a few people recently.
I dig them both.
Contact Mirror Trick Shot: https://youtube.com/watch?v=sCTGdhXCSks&feature=emb_title
It is two images composited together:
1) One shot is of a mirrored medicine cabinet (with the mirror covered in blue) with the character's hand reaching to it.
2) The other shot is the character running.
The running shot is composited into the cabinet shot via a blue screen keying effect.
It is a mind bender.
Props to Robert Zemeckis and the whole team on this one.
Props to the guys below for a visual breakdown. I agree with what he says in the video; it's a good reminder that simple effects can be very powerful.
(words are original. image is open and free use from pixabay. posts may also be shown on my hive.blog page.)