FREEZE AND JUSTIFY
The group sits or stands around the acting space.
Two people enter the space and begin to improvise a scene, with dialogue and as much physical action as possible.
At any moment, anyone else in the group may shout, "FREEZE!"
The actors freeze instantly and exactly.
The person who stopped the scene taps one of the actors on the shoulder. That actor sits down and the new person takes his or her position exactly.
The new person must now initiate a new and DIFFERENT scene. The scene must flow naturally from the positions of the two bodies, and it is the new person's responsibility to communicate to his or her partner and to the audience what the new scene is about.
At any moment another person may shout, "FREEZE!" and it begins again.
It may be necessary to make a rule that no one may freeze a scene until the situation has been clearly established and both actors have contributed.
A way of insuring participation by all is to have students take turns saying, "Freeze!", such as going one by one around the circle.