I'm the most mellow person offstage. I think it's just, going onstage lets me get out some frustration that I'm too shy to do in real life. Instead of doing it in private, I'd rather do it in front of 1,000 people who've paid $25 to see me lose my mind.
In stand-up you can go either way. It's live. Somebody might say something in the crowd, you might respond to it. But in a movie you could be spontaneous too. But you pretty much have to stick to that story or that scene or that script, but in stand-up you can go wherever you want to. It's more freedom.