The film's soundtrack became an unlikely blockbuster, even surpassing the success of the film. By early 2001, it had sold five million copies, spawned a documentary film, three follow-up albums ("O Sister" and "O Sister 2"), two concert tours, and won Country Music Awards for Album of the Year and Single of the Year (for "Man of Constant Sorrow"). It also won five Grammys, including Album of the Year, and hit #1 on the Billboard album charts the week of March 15, 2002, 63 weeks after its release and over a year after the release of the film.
About 350 extras were hired for the Klan rally sequence. Many of them were members of a military formation troupe, and many were African-Americans! Joel Coen later recalled hearing one say, 'This is the freakiest thing!'
Although Homer is given a co-writing credit on the film, Joel Coen and Ethan Coen claim never to have read "The Odyssey" and are familiar with it only through cultural osmosis and film adaptations.
According to Joel Coen, there was a snake catcher on set. "We hired this guy and he came to set with a golf club and what he would do is he would look around for snakes. If he saw one he would rope it with the golf club and put it in this bag. I asked him what you called somebody with this profession, and he said, 'An idiot.'"
George Clooney practiced his singing for weeks, but in the end his singing voice was dubbed by bluegrass singer Dan Tyminski.
Joel Coen: [fricassee] Dan Teague tells Everett "Thanks for the fricassee," in the picnic scene under the tree. Joel Coen and Ethan Coen also included this dish in Fargo (1996) when Margie and Norm are eating in a restaurant and another cop asks her, "How's the fricassee?".