I did not realize until I posted a Vintage Image of the Day for Shock Treatment that the "not a sequel" to The Rocky Horror Picture Show was one of my favorite guilty pleasures. Two days after I posted the photo, I bought the DVD and threw out my old VHS copy, so I can enjoy the highest resolution, most gorgeous images and sound possible when I indulge my secret love for the 1981 cult classic.
In my Vintage Image of the Day post, I called Shock Treatment the sequel to Rocky Horror. As others have noted, this isn't strictly true. However, some of the characters are the same. Remember Brad Majors and Janet Weiss? (Keep your audience-participation nicknames to yourself.) In Shock Treatment, the happy couple is now married, but something's wrong with their relationship, something they themselves can't quite express. The characters are played by different actors -- Cliff De Young and Jessica Harper take over the roles held by Barry Bostwick and Susan Sarandon in Rocky Horror. On the other hand, cast members from the first movie also appear in Shock Treatment, but as different characters.