"I did play a dentist in Waiting for Guffman. I wrote the speech at the conference. In the original script, when it got to that scene, it was, 'Thank you very much. Good night.' Literally. I just thought, 'He keeps talking about this speech. The keynote address is the big thing in his life and this is too important to say, "Thank you. Good night." I think we have to see and hear him doing what he does.' So I got together with my dentist and we worked through a few things."