2 (or 4)
If using audience members they will occasionally shout out words.
Two actors are given a scene with two other actors or audience members standing off to the sides of the stage. These volunteers on the side, the pillars, are blindfolded and given ear plugs so that they cannot see or hear the scene that's happening. As the playing actors go about their scene they'll occasionally touch one of the pillars who will then shout out any word that comes to mind. The actor who touched them must then use whatever word was spoken in their next line of dialogue to continue the scene.