According to the interview with Paige Conner on the Code Red DVD, Shelley Winters smacked Conner for real several times while both rehearsing and filming a key confrontation scene with her.
Paige Conner wore a bald cap for her scene in the greenhouse. All the other kids in the greenhouse scenes had their heads shaved.
Paige Conner had trouble saying harsh profanity to Glenn Ford in her big confrontation scene with him.
Sam Peckinpah had trouble remembering his lines. Because of Peckinpah's difficulty with his dialogue, his voice was dubbed by another actor.
According to Lance Henriksen, the cast agreed to do the movie to get a free trip to Italy. Henriksen dislikes the movie, calling it "a real turkey."