Allocate each person in a circle to look at, so that everyone is looking at someone and everybody is being looked at by someone.
Instruct each person to really observe the person they are looking at and to imitate any movements they do.
Keep encouraging the group to stand still.
You will find that in the circle there is continual movement and it is almost impossible for it to be completely still for any period of time
Tell the circle to exaggerate any movements they see and the circle will quickly become very animated.