During the scene in the antique shop, the owner asks Marvin "do you remember that band Satan's Claw" This refers to the Tigon film The Blood on Satan's Claw (1971) co-produced by the director's uncle Peter L Andrews.
In the credits the policeman who interviews Marvin is called Detective Chetwyn. This is a nod to the writer R. Chetwynd-Hayes credited as the story writer of From Beyond the Grave (1974), one of the director's favorite horror films.