Free Truth in Comedy: The Manual of Improvisation by Charna Halpern, Del Close, Kim Johnson

choices to continue the action.
    If something unusual or unexpected occurs, an inexperienced actor sometimes ignores it, thinking it isn't important because it's not in line with what he thinks should be happening. Wrong! The actor entering the scene, the audience, and even the other actor may all be expecting a pizza — indeed, it's probably the most appropriate move — but if one actor decides the man is delivering manhole covers, then he is right, and everyone must immediately accept it.
    Everyone might initially view this as a mistake, but the only true mistake is for the other actors to ignore or negate him, and turn manhole covers back into a pizza. So the actors must justify the line, and can only do so by being in the moment. Remember, if everyone justifies everyone else's actions, there are no mistakes.
    That unexpected line could be the interesting twist that shapes the scene right before the players' eyes. The pizza delivery is appropriate and expected, but the arrival of a person with manhole covers is guaranteed to make the scene more interesting!
    After all, a scene is almost never about what the players think it's going to be about. Once underway, the actors follow the scene along, but they shouldn't try to control it. The scene is the result of the relationship between the characters, and the relationship that grows from those explored moments.
    Nothing is ignored.
    Nothing is forgotten.
    And nothing is a "mistake."
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THE REASON WHY
    Since one of the most important responsibilities of an improviser is justifying what his fellow players say and do, everything that happens on stage is used to build the scenes — so there can't be mistakes if it's all accepted.
    Of course, not^vgrything needs to be justified immediately. Everything heard should be remembered and eventually used; the players will make sense out of it before the scene is over. One of the primary uses of discovery is finding how some seemingly confusing element introduced early in a scene (and apparently forgotten) is found to have a vital place in the denouement.
    One of the surest audience-pleasers in an improv scene is also one of the easiest to accomplish. A crowd delights in seeing a player pull out a forgotten scenic element just in time to solve a problem — like a chess player suddenly executing a checkmate, apparently out of nowhere.
    An example of delayed justification is a scene between Mary and Robin. Mary looks over her doll collection, while Robin is sitting at a desk, engrossed in figuring out bills.
    MARY: "I can't figure out why I keep finding the heads torn off my dolls."
    ROBIN: "You owe me fifty dollars for the phone bill."
    MARY: "I don't have the money for my share of the bill."
    (The pair starts quarreling, until Robin gives up in frustration. Finally, she calmly walks over and tears the head off a doll.)
    The two of them were able to justify the opening line brilliantly (although the ending of the scene appears obvious on paper, it is something else entirely when the audience watches it being created). The scene was not about pulling the heads off dolls; it was about the frustrations of two roommates. In improvising the scene, the players discovered the past his- tory of their relationship. The missing heads obviously indicate that Robin has been frustrated by her roommate in the past, and allows for some interesting possibilities if the scene is continued in the future.
    An actor can only justify scenic moves — and any seeming "mistakes" — if he is "in the moment," and not planning ahead. Two easy exercises to help develop this are the Conducted Story and the One-Word Story.
    ONE-WORD STORY
    The One-Word Story is one of the simplest of all improv exercises, and very useful for teaching the importance of staying in the moment.
    Here, a group of players (usually six to eight) build a story one word at a time. The basic method sees the actors line up on stage and, beginning at one end, each speaking one word, forming