Leandro frequently having a lolly pop in his mouth was a trait added by Telly Savalas. Savalas had recently quit smoking and used the lolly pops as an alternative. The lolly pops would become a popular character trait on his American television series Kojak (1973) which started that same year.
The scene where Leandro breaks the corpse's feet to stuff it into the coffin is a reference to the H.P. Lovecraft story "In the Vault".
Surprisingly there was no luck in getting a distributor for the film, even after successful screenings at film festivals. Ultimately in a desperate attempt to get the film into theaters it was heavily re-edited with newly shot footage involving a priest and a possessed Lisa. It was sold under the new title The House of Exorcism (1975) in an attempt to cash in on the success of The Exorcist (1973). Bava's original film, "Lisa and the Devil", also received a very limited theatrical release, as well as appearances on TV.
The film was shot without sound and the dialog was dubbed in after principal photography. Reportedly while directing the cast on the set Bava would play Rodrigo's "Concerto d'Aranjuez" to get the emotion he desired from the actors.