This improv comedy game can be made a little bit harder by changing the rules just a bit. First the scene starts with only one person. He/She is given an action. The actor then poses this action and freezes and then the very same actor can define his/her action again. The actor starts to act and any other actors "in the audience" can yell "Freeze!" and the actors on stage must freeze. The yeller then assumes a completely new position and a new scene is created.
This is continued until the maximum actor number is reached (good values for this are 4, 5 and 6. It's very difficult to make a good scene with 6 people on stage). At this point the actor start to leave. The last person who came on stage leaves first. The leaving must be justified.
This exercise is great for warm-up!
btw. My teacher called this game "Jähmy" in Finnish...