Originally titled Pajama Party in a Haunted House, this last of the beach party pictures from AIP (although there's no beach, just a pool), left AIP unhappy after wrap-up, so Boris Karloff and Susan Hart were called in to film scenes that would be added into the movie (Wikipedia). Annette Funicello and Frankie Avalon didn't make it into this one, although they appear in the other six beach movies.
