The Clerk of the Court at the U.S. Supreme Court put out a very helpful guide for lawyers who will be arguing before the Court that contains this anecdote:
One counsel representing a large beer brewing corporation was asked the following by a Justice during argument: “What is the difference between beer and ale?” The question had little to do with the issues, but the case involved the beer brewing business. Counsel gave a brief, simple, and clear answer that was understood by everyone in the Courtroom. He knew the business of his client, and it showed. The Justice who posed the question thanked counsel in a warm and gracious manner.
Seems to me there are two possible lessons here. First, always prepare for oral argument. Second, know your beer.