Teddy Wilson, I think, said a little while ago that it's much easier to come in and play whatever comes into your mind, without obeying any of the laws of bass line and harmony and so on.
Once you start thinking about it in a mercenary frame of mind, then you're finished. You're a joke, because there are too many mercenaries out there already.
I was doing Hamlet in the off-season, and I had a specific idea in my mind about what I wanted that character to look like, and because it's going to lead into the next year, I knew that it was going to have to be established somewhere in the show.