There's an old story about a terrible production of the play The Diary of Anne Frank.
It's the stage adaptation of the heartbreaking and inspiring diary of a young Jewish girl in Holland who, along with her family, hides in the attic of an Amsterdam house during the Second World War.
This particular production of the play was so awful, apparently, that in a scene early in the first act, when the Gestapo comes to search the house, someone from the audience called out: "They're in the attic! They're in the attic!"
Everyone, as we say here in Hollywood, is a critic. What that one displeased audience member did in person, thousands of folks do every day on blogs, Facebook updates, and tweets. Twitter, in fact, has a measurable effect on the weekend box office of new releases - what used to be called "word of mouth" advertising is now called the "Twitter effect". A movie that gets a lot of bad tweets on Friday night can wither away by Monday morning.
Still, it's a lot easier for an audience member to ruin - or maybe, enhance - a live performance. We're so isolated from real-life groups these days - we watch movies on our big flat screens at home; we interact via Facebook and e-mail - that it's hard to remember a time when the actual, living and breathing audience really mattered. Personally, I still love to watch horror movies - especially slasher movies - in big theatres. Somehow, it's less scary, less weirdly violent. I feel better about myself, in other words, sharing the jumps and the jolts with a lot of strangers - even strangers who talk back to the screen - than sitting at home, on my sofa, watching a guy with an axe chase a girl around. With others, it's fun. Alone, it's creepy.
Audiences, though, can also ruin a moment. I've worked on television series where we've actually had to remove from the soundtrack the laughs that came from the live audience because they seemed to come at the wrong time. It hurts to remove laughter from the track, but when it smothers a line or gives away a moment, you have to swallow hard and do it. Years ago, live audiences started reacting with over-the-top "oos" and "ahs" to certain moments in television episodes, and it didn't matter where you were - in the studio, at home - it all felt oddly disorientating, as if the audience were composed of malfunctioning robots.
And we've all been in the theatre when someone's mobile phone has gone off, right in the middle of a crucial scene. Years ago, a friend of mine went to the big New York premiere of the movie The Elephant Man. Anthony Hopkins plays a sympathetic and compassionate doctor who rescues the poor, deformed, physically shocking Elephant Man (played wonderfully by John Hurt) from a life of exploitation in freak shows and circuses. The Elephant Man's life, before meeting up with Anthony Hopkins, is miserable and dehumanising, an endless parade of cruelties and abuse.
It's a great, dark, vivid picture, and it has a wonderful moment near the end when the Elephant Man - with his huge, deformed head and twisted-up face, drooling mouth and offset eyes, is invited to meet the Queen of England.
The kindly Anthony Hopkins presents the Elephant Man with a suit, and through the bumps and protrusions on his head, you can see his terrified, proud eyes. He puts on his white tie and tails, looks at himself in the mirror - his monstrous, contorted face, flecked with spittle, his eyes bugging, but looking from the neck down like a perfect Victorian gentleman - and he turns to Anthony Hopkins and asks in a hopeful, quivering voice: "How do I look?"
Your heart breaks. In the theatre, you can hear a pin drop. The audience is awestruck by the power and pity of the moment.
Except for my friend. At the New York premiere of the film, when the Elephant Man turns his grotesque face to ask "How do I look?" my friend couldn't restrain himself. He called out: "Honestly?"
Silence. Then laughter. Then the spell is broken. For the movie to work, you have to believe that at that moment, the Elephant Man is handsome. My friend ruined that moment - for everbody in the cinema.
Which serves as a reminder for everyone in show business, and probably every other business, too: we can write and act and direct as brilliantly as we can. But it doesn't matter. One wise guy in a quiet theatre can take it all down.
Rob Long is a writer and producer in Hollywood