On the DVD audio commentary, David Simon recalled Neal Jones's somewhat unorthodox audition for the role of Sgt. Major Sixta. According to the story, Jones entered the audition room, immediately began screaming his lines unintelligibly - much like his character does - and then walked out of the room without another word. As he opened the door to leave, he winked at casting director Alexa L. Fogel, and she realized she had the right actor for the role.
Alexander Skarsgård is an actual military veteran, did his conscript in Sweden's equivalent to the U.S. Marine Corps.
Rudy Reyes (the muscular marine who runs around the camp with a gas mask on) portrays himself in the TV series.
The real life Sergeant Major John Joseph Sixta was convicted to 30 years in prison to life for abusing his 2 stepdaughters in California when they were children. He was convicted too in Arizona for abusing another child and was sentenced to 10 year in prison.