Divide the group into pairs. One of the players plays the mirror image of the other. The ‘original’ moves in slow motion. The goal of this exercise is not to make it as hard as possible for the mirror image, but to make the mirror image and the ‘original’ form one whole.
Variation: Both players are mirror image and ‘original’ at the same time. It is also possible to do the exercise with more than 2 players in a circle: everyone mirrors each other.