This film finished production in 1999, and its original release date coincided with the Columbine High School shootings. The release was postponed because of the film's themes of violence and murder in a high-school setting.
Some post production sound was provided by students at Sir Francis Drake High School in San Anselmo. They added their sound to the basketball crowds, party fight scene, and the shooting scene in the girls' dorm.
Although released in 2001, the film was actually filmed in 1998. This is the second film in which Julia Stiles appeared to be released three years after it was filmed. She previously appeared in M. Night Shyamalan's Wide Awake (1998), which was actually filmed in 1995.
The studios were initially hesitant about giving the film a one-letter title. The original title was "Odin". But they eventually decided the one-letter title was better because it was unique. The "O" also resembles a basketball hoop, which Mekhi Phifer appears to be holding on the poster.