The same subject matter was later revisited in The Doctor and the Devils (1985) and the Simon Pegg-Andy Serkis starrer Burke and Hare (2010). Burke and Hare are also characters in Dr Jekyll & Sister Hyde (1971).
Françoise Pascal said she was working on the horror film Blood Suckers (1971) when producer Guido Coen visited the set. Suddenly she heard him shout, "I found my Marie, I found my Marie!" and he started pointing at her. She found out he had been looking for an actress to play Marie in this film for a long time and knew he had the perfect one when he spotted her.
Glynn Edwards and Yootha Joyce, who played Mr. and Mrs. Hare, had been husband and wife in real life until they divorced in 1968.