The website The Smoking Gun likes to locate and post "riders" for acts that tour around the country. These are the portions of a contract that specify the non-financial details of the act's appearance — how the dressing rooms are to be set up, what kind of catering there will be, etc. In some cases, the demands are exorbitant or silly…but also, like the secrecy clauses in David Copperfield's rider, understandable.
Recently, they finally got their mitts on what they call their "Holy Grail" of such documents — the famous Van Halen rider in which the group demanded that the candy dishes backstage contain M&M candies but no brown ones. It is now possible to buy M&Ms by color so that request would be easily-filled today…but back then, it meant someone had to go through the bags and remove the brown ones, and the clause was oft-cited as an example of rock star arrogance. The explanation is offered that the demand was inserted just to see if the promoters were paying attention but I dunno…