In the scene in the chess club, when the chess coach points out famous chess players to Josh's father, all the players are actually playing themselves (Joel Benjamin, etc).
Max Pomeranc, who plays Josh, is himself a strong chess player. At the time this film was made, he was ranked among the top 100 in the nation for his age group.
The movie includes cameos by the real-life Bruce Pandolfini (kibitzer in the park) and Katya Waitzkin (girl ranked 82nd in the national championship). The real Josh Waitzkin was a consultant for the film but does not make an appearance on-screen.