In an interview on National Public Radio's "Fresh Air," Chiwetel Ejiofor said that he thought he'd challenge David Mamet to a friendly sparring match (keeping in mind Mamet had been a practitioner of jiu-jitsu for some years compared to Ejiofor's training for a few months). They squared off, and Mamet stepped on Ejiofor's foot with all his weight. Ejiofor couldn't free his foot and was vulnerable to attack. Mamet said words to the effect that "This match is over."
In the stadium fight scene, David Mamet handed out $100 bills to background in the stands if they answered trivia questions correctly in order to get them to look in the right direction and "appear" interested.