Killer Whales have no concept of “no.” At least, of course, as far as we know. So it’s hard for a trainer at Sea World to get them to do the things that they want. A trainer can’t say “no” when a killer whale does something wrong… wrong is a concept that doesn’t even exist only in the whale’s mind.
A good trainer instead focuses on and enhances the behaviors that are already there. A killer whale can naturally jump out of the water, so a good trainer will find a way to tap into that natural behavior and get that whale to jump. Eventually, the unwanted behavior falls away.
Similarly, a coach or director can do the same to their performers. Praise them. Point out the things they did that you liked. Give them things to do, instead of what not to do. You will strengthen those natural tendencies they have that make improv work, and eventually the rest will fall away.