One of the things that is always difficult about a collaboration is that you don't necessarily find the same thing funny. And so the challenge becomes, how do you tell the other person that you don't think something's funny? The best collaborations tend to be when you are willing to be told that. But there's also ego involved, and so there's a lot of frustration in knowing that you're writing something, and the other person, on some level, needs to think that it's funny.