In any interactive theater it is essential to develop the improvisation skill known as "Justification," the ability to make sense of anything by weaving it into the tapestry of a scene as a whole. In its simplest form, it means finding or making up a reason for anything that happens. Actors do this all the time as they study a script for input as to a character's motivations for what he does. Find a reason for why Joe looks out the window when he does and you have justified the action. Learn how to find a reason why a weasel driving a '65 Chevy might run through the window and you're on your way.
If, as Elaine May (and letís not hold directing Ishtar against her here) has said, "The actor's job is justification," then the improviser's job is justification on the fly. So, how do you do it? By making connections. Essentially, you look for a way to tie the new element in to whatever has gone before, no matter how tenuous the connection may be.
Suppose, in a tense moment as one character pulls a gun on another, a waiter drops a tray. Go ahead and work it in by connecting it to what's going on. "What are you worried about? He's pointing at me!" Or if at that same moment, say someone in the audience loudly asks a waiter if the coffee is decaf. "Great. I'm gonna die, and she's worried about getting to sleep tonight."
The improvisation game "Hesitation" is a good one to rehearse in order to develop justification skills. In this game two or three actors act out a scene, such as an historical event, but pause every once in a while they hesitate, as if they have forgotten a word and need the audience to supply it. Whatever one of the spectators shouts out is what they have to use, justifying the word and continuing the scene.
A typical game might go like this:
Solder: "General Washington, will you sit down? You're rocking the boat."
Washington: "Sorry, but I have to keep an eye out for British . . . um, British . . . you know . . ."
From crowd: "Cheeseburgers!"
Washington: "British cheeseburgers! You know, the men are starving at Valley Forge, and they need all the food they can get. I heard the Redcoats were shipping food across the Delaware, and we've got to get it!" (The totally foreign idea of cheeseburgers is brought into the scene and made a part of it.)
Solder: "Good idea, sir. If I'd known this was such an important mission, I'd have brought a real oar to paddle with, instead of this . . . uh, . . . uh . . ."
Crowd: "Wet noodle."
Solder: "Wet noodle. I mean, you can paddle with dry, hard spaghetti on a short trip, but once it gets soggy and goes limp, you're going nowhere."
And so on. After sufficient practice it should become easier to take any comment or event that gets thrown into any scene and make sense of it. Instead of fighting anything outside of the script simply invite it in to the scene, make it a part of the overall goings on, and then get on with the show.
If the audience is to be allowed to question the characters each actor must know the details of the entire piece, not just their own lines and cues. If a character gives an answer that contradicts something else in the script the audience will notice, and, what's worse, assume that it's a clue. They must also know what their characters would not know, so as to be able to answer, "I don't know, you'd better ask Freddie," and then react appropriately to Freddie's answer.
Some members of the audience may be so concerned with solving the mystery that they assume everything is a clue. They will literally be watching your every move, so be sure your movements and business are motivated and in character.
Even subtleties may be picked up on: in one mystery I participated in, we were surprised at the number of people who had noted on their clue sheets suspicions that the lovely heiress was having an affair with the sleazy lawyer. The characters were supposed to be doing nothing of the kind -- but the actor and actress playing them actually were dating in real life, and some of that interplay between them came through. Similarly, audiences sometimes pick up on the real life mother/daughter relationship between two On The Edge actresses, even though their characters in one play didn't even interact with each other (although the actresses might have during breaks.) If you're on stage -- be in character.
Next Step: Handling Hecklers.
The Elaine May quote above is from her interview in
Something Wonderful Right Away,
a wonderful book I highly recommend to anyone interested in Improv Comedy.