Pushing the envelope' sort of implies that you're inside the envelope with everyone else, and you're trying to find the edges on the outsides.
Louis C. K.Comedians work great as actors because they're good under pressure. With a lot of actors, you have to make them feel like everything's going really well to get a good performance out of them. But, if you have a comedian on the set, you can tell them, 'Hey, you really are screwing this up,' and then they just get better.
Louis C. K.