Dwayne Johnson's stunt double in this movie, his cousin Tanoai Reed, was nominated for and won the award for Best Overall Stunt by a Man at the 2004 Taurus World Stunt Awards.
Dwayne Johnson's body double was his cousin. He broke his ankle in the scene where Beck and Travis are tumbling down a hillside with the Jeep.
According to Seann William Scott the "thunder and lightning" bit was just a joke, but was so entertaining it was kept in the film.
According to director commentary on the DVD, Christopher Walken had never seen Willy Wonka & the Chocolate Factory (1971) and was therefore reluctant to use the phrase "Oompah-loompahs" in his final scene. Director Peter Berg provided Walken with a copy of the movie, and after watching it, Walken decided to use the phrase.
Dwayne Johnson accidentally sliced Seann William Scott's arm open with a knife that was supposed to be a blunt prop knife but wasn't. Although not seriously injured, Scott still required several stitches.
Arnold Schwarzenegger: as a man in the club. This cameo was filmed the same day he filmed his appearance as the Terminator for the Super Bowl. It was completely unprepared. He happened onto the set that day and was asked to make a quick appearance in the film. Fans and movie enthusiasts often cite his saying "Have fun" to Dwayne Johnson as a passing of the torch to an action hero of the next generation.