Bobbie Bresee revealed on the commentary of the BCI DVD release that she received some possessed voice coaching from Mercedes McCambridge (notable for the demonic voice in El exorcista (1973)) while co-starring with her in "Charlie's Angels" (1976) Angels in Springtime.
It was produced by the "Yuppie Don" Michael Franzese, former capo of the Colombo crime family. It was allegedly a form of money laundering. Wether it was a passion for film or simply a business venture is unknown.
The scleral contact lenses that Bobbie Bresee had to wear during some possessed scenes damaged her eyes. This damage resulted in her filming some scenes towards the beginning of the film without her eyesight.
When BCI Eclipse obtained the DVD rights to the film, they couldn't find any original elements to transfer. Forced to use a damaged print, BCI decided to release it as a double feature.
On the DVD commentary, Bobbie Bresee revealed that producers set up bleachers for crew members to watch the filming of her sex scene.