You don't have to be quick, just clever. It might sound dumb written, but here is an example. One of the skits was of a girl trying to get people to help her unlock her car door because she locked her keys inside. One guy just pretended to be retarded (which is a cop-out), one girl pretended like she was too ditzy to understand. Then she asked me, "Can you pop the lock, sir?". So I just started pop locking on stage and kept saying "IS IT WORKING?!?! IM POP LOCKING RIGHT. NOW. I AM DOING IT. RIGHT. NOW."For what it's worth I don't think I could cut it at Improv. I'm usually quick and off the cuff, but I think you need more than that to be good at it. I just think I'd be that awkward one everybody wants to boo.
I guess the point of this post is to say its not about being funny or "right", just about being able to make something of a situation quickly...if that makes sense?