Scenes from "The Slumber Party Massacre (1982)" were used for the flashback sequences just to add to the runtime. This was before the title was changed to "Sorority House Massacre II", which is why footage from the original wasn't used.
Written and shot in seven days.
This is a sequel in name only. It was conceived by Jim Wynorski when he discovered sets used for Slumber Party Massacre 3 (1990) and Rock and Roll High School Forever (1991) were going to be demolished in Roger Corman's studios. Wynorski heard Corman and his wife, Julie, were going away to Europe for a week, so he quickly pitched the idea of shooting a slasher movie to Julie. She put a hold on striking the sets and told Wynorski to make the film while they were gone without telling her husband. Wynorski wrote the script in four days, cast it in two, and started shooting the moment they left town. He made it under the title Jim Wynorski's House of Babes in just seven days with no producer supervision. Roger Corman only got wind of it after they returned and was pleasantly surprised with how well the film turned out. The title was changed to Nightie Nightmare but then the Cormans decided that it would sell better if it were a sequel to an existing film, which is why the film has nothing to do with the original Sorority House Massacre film there while she and her husband were out of town, only under the condition that Roger not find out. It was written, cast and filmed under the title "Jim Wynorski's House of Babes" in just seven days with no producer supervision. Roger was pleasantly surprised with how well the film turned out.
The end credits verify, "No girls were actually harmed or mistreated during the making of this film".
Filmed across the street from the house used for The People Under the Stairs (1991).