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 Wynoraski when he noticed some sets were available in Roger Corman's studios. He was given permission by Roger's wife, Julie Corman, to 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 title was changed to "Nightie Nightmare" before the Cormans decided that it would sell better if it were a sequel to an existing film, hence why the film has nothing to do with the original "Sorority House Massacre".
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).