Matt Damon and Edward Norton played the $10,000 buy-in Texas Hold 'Em (No Limit) championship event at the 1998 World Series of Poker in Las Vegas. During the first of four days, Matt Damon had pocket Kings and was knocked out by former world champion and poker legend Doyle Brunson who held pocket Aces.
On the DVD commentary it's revealed that Edward Norton ad libbed a number of Worm's lines. Among them was, "She crossed her legs too fast," which is a quote from Chinatown (1974).
Matt Damon said in an interview that getting John Malkovich was a big deal for the film, so much so that on the first take John Malkovich did a very cartoonish and over the top performance at the end of which the whole crew applauded and praised him for how brilliant it was. At which point Matt Damon looked John Malkovich very confused, John Malkovich seeing him looking confused leaned over and said "I'm a terrible actor." Matt Damon said John Malkovich was trying to show him that "if you get to that point where no one gives you a straight answer, it's dangerous"
Early on, Mike is seen taking money out of a poker book called "Super System", which was written by poker legend Doyle Brunson. He later pulls quotes from the book with the lines "Texas Hold 'em is the Cadillac of poker games" and "The trick to no limit is to put a man to a decision for all his chips."
Brian Koppelman: Writer can be seen at the Atlantic City poker table smoking a cigarette just as Matt Damon is describing smoking as a tell.