Hannah, the three-legged dog used in this movie, was cast from a local dog agency, and she had lost her leg after saving her master in a robbery at the pub that she lived in.
Dialogue for the film was written by Fay Weldon. "In the original script, the girls were ciphers. I gave them characters, which had the unfortunate effect of turning the film into a cult movie. I should have left it as it was. Picture dialogue: A. Picture movie: D. A terrible mix."
Film debut of Joanne Good. She was 23. Good said in an interview years later she took the role because it required nudity which she was anxious to do since she felt it helped the careers of Britt Ekland and other actresses. But, to her disappointment, she was never asked to take her clothes off, even though the other actresses playing schoolgirls were. Closest she got was to have her nightgown ripped open, but nothing was exposed.
The scene with the cat having its tail cut off by one of the escaped lunatics was improvised when it was discovered the cat was already missing its tail.
The bulk of this movie was shot in sequence.