“Oh, I wish Jack was here. Jack’s great. He’s got that funny hat and always has a joke. He’d make it fun.”Obviously, this is clearly a call for Jack to come on and save the scene, which is usually what will happen. But while the description is happening, it’s not so interesting because Jack’s not there. If the actors had talked more about their relationship it would not only be more engaging but also we’d have no need for Jack.
Improv does best with the “show, don’t tell” principle, so talking about Jack is not as interesting as having Jack there.
|Jack not needed here.|
It becomes clearer to explain if you substitute the person for an object. Take the two friends one of whom stole the other’s girl. If it wasn’t a girl, but a car that was stolen, the scene could proceed very much on the same lines. But even then, it would be better if the car was there because the actors could use the physicality of the car to help them find and express their emotions.
So if we make it something more abstract then I think it is even clearer. If what was stolen was leadership of the book club, for example, then we see the function this third person. And although the emotions attached to the object might be slightly different, the scene is still about betrayal and possibly rivalry. And in this version, it makes it clear the scene could be seen as being about status.
So in short, there are times when discussing someone outside the scene is fine. As long as it doesn’t become simply a long description of this other person and their antics, and remains ultimately about the relationship between characters there on stage.