We enter a scene only to serve what is already in play. We enter to heighten a Personal Game. We enter to heighten a Scenic Game. We may help our fellow players by focusing them on one aspect of the scene when they’re juggling too much, but in that effort we are focusing on what is already an aspect of the scene.
We don’t enter with a self-serving funny idea that risks derailing the central players’ progression. We don’t enter with totally new information that players on stage now have to address and deal with. We don’t enter just to selfishly get in on the fun because the scene might have been fun precisely because you weren’t in it. We don’t help players on stage by changing the direction of the scene; if players were struggling with what they have, they aren’t likely to seamlessly adapt to your idea however brilliant.
We wield a slew of tools: Walk-Ons, Cut-Tos, Tag Outs, etc. Brandishing these tools in service of what’s already in play we recognize that we must also be ready and willing to draw out Walk-Offs, Cut-Backs, Tag Back Ins, etc. Entering a two person scene in progress, you are a tertiary player. The scene’s not about you and you shouldn’t make it about you.
An improv team should agree to this Tertiary Player Good Faith Mantra: I will only enter a scene in progress to serve what has already been established. And I will react to those who enter my scene in progress on the assumption they seek to heighten what has already been established.