Keeping it Real

Johnny starts a scene in a collection around the motif of "rock." He puts a mimed guitar around his neck, tunes it and them plays some notes with haunting feedback. He provides the noises himself. The audience is in awe. Charlene enters and says, "Why are you playing that invisible guitar?"

Actually this mime isn't so great.
Look how thin that guitar is. 

The audience laughs. It's a classic standup-style gag. Set it up and break it. Funny, but very destructive to the scene. Johnny has trouble continuing with the scene because Charlene blocked his clear offer of his character playing a real guitar. And his character has gone from being a rock guitar god to a delusional crazy person. What's more, Charlene now doesn't know what to do after her initial gag. The guideline here is: Treat mimed objects as real. Otherwise we are reminding the audience this is all fake.

And whilst the audience laughs, I think it's with a little regret. Certainly any of them who has had some improv training will feel that. The audience will probably feel a little cheated. As if Johnny roped them into his world with his great commitment, miming, and sound effects only to have it thrown back in their face. Stupid you for believing that was real. But if we reinforce the reality of these objects, the audience can be brought in further, their wonder used to fuel great a story and, on the way, we can tell better, less disappointing and destructive jokes.