What was the spin-off movie to The Rocky Horror Picture Show?

Shock Treatment is a 1981 American black comedy musical film directed by Jim Sharman, co-written by Sharman and Richard O'Brien, and a follow-up to the 1975 film The Rocky Horror Picture Show.

While not an outright sequel, the film does feature several characters from the previous film portrayed by different actors and several Rocky Horror actors in the roles of new characters. The film stars Jessica Harper as Janet and Cliff De Young in a dual role as Brad and the film's main antagonist Farley Flavors, with O'Brien and Patricia Quinn as sibling character actors.

Given in a limited release on the midnight movie circuit beginning on October 30, 1981, Shock Treatment was a critical and commercial failure, not earning the same level of cult film status its predecessor received. Still, it has a minor following. In 2015, the film was adapted as a stage production in London.