That's just at a bare minimum, though. Mr. Williams would prefer that two framed photos of the astrophysicist in his dressing room.'I watched 'Cosmos' as a child and I was always blown away by Sagan's mind and the way he thought," Williams told The Today Show last June. 'When I look at that picture I realize how lucky we all are--to be on this planet and be able to do what we love to do every day. Seeing Carl's face reminds me of it."

For those who don't know, a tour rider is a list of the items that an artist requests of the concert promoters in each city they're playing. Typically, the lists consists of otherwise mundane items like clean towels, specialty foods, full-length mirrors, Internet connectivity etc. But some artists enjoy adding items to the list for comedy's sake.