Scene 6: Hope, Gerald, Prof. Petrie (anal)
The bookworms are reading the miracles of the newly-acquired Necronomicon, when Hope enters and gets interested. Since both of the twin whores know who's fucking who, a little mistaken identity ensues, and soon everyone knows.

You obviously caught the connection of Dick Van Dyke and a movie about lesbian sisters. Through much of the 1970s, lesbianism was considered a psychological disorder, and was often treated with drugs.

Shortly Hope is tasting the board of education while Daddy bangs his other stepdaughter...in the ass, of course.

The "Necronomicon" was an invention of horror writer H.P. Lovecraft. It's not a real book, but that doesn't stop the English majors from Yale putting fake reference cards for it in the Yale Library once a year, those crazy dorks.