(at around 46 mins) Otis' line "I am The Devil and I am here to do the Devil's work" is a slightly altered version of a quote spoken by Manson Family member Charles 'Tex' Watson during the infamous Tate Murders.
Sheri Moon Zombie's brother has a cameo as a police officer in the opening shootout scene. He was originally only on the set as a visitor, but director Rob Zombie put him in the scene because he knew how to handle firearms well.
Around 100 digital effects shots appear in the film, mostly to create gore. The scenes involving objects coming into direct contact with skin (like throat slitting, people getting shot in the head or neck, or stabbings) were created digitally. The violence that didn't involve direct skin contact (like people getting shot in areas covered by clothing) were achieved practically. Rob Zombie originally intended to create all of the special effects using only techniques available in the 1970s, but time constraints prevented this.
Karen Black demanded a higher salary to reprise her role as Mother Firefly. Director Rob Zombie could not afford to increase her pay and decided to replace her with veteran actress Leslie Easterbrook.
Rob Zombie stated in an interview that, up until 31 (2016), 'The Devil's Rejects' was probably the hardest film of his to cut down in order to receive an R rating.