Question: Who directed the 1975 British-American musical screwball comedy horror film to which "Shock Treatment" Is a follow-up film?

Context articles: Rocky Horror sequels and other media
The Rocky Horror Picture Show
Shock Treatment (1995 film)
Shock Treatment
Blair Witch (film)
AFI's 100 Years...100 Laughs
The Terror Factor
Jim Sharman
The Irony of Fate
Jessica Harper

"The Rocky Horror Picture Show" is a 1975 British parody musical comedy that satirizes science fiction and horror B-movies.
 It was one of the first successful midnight movies and has gained a cult following.
 Because of the cult following, it has spawned an indirect sequel "Shock Treatment", as well as merchandise such as video games, toys, comic books and trading cards.
 Richard O'Brien has also attempted (and failed) to write scripts for movies and plays to further the story.
The Rocky Horror Picture Show is a 1975 British-American musical screwball comedy horror film by 20th Century Fox produced by Lou Adler and Michael White and directed by Jim Sharman.
 The screenplay was written by Sharman and actor Richard O'Brien, who appears in the film, which is based on the 1973 musical stage production "of the same title", with music, book, and lyrics by O'Brien.
 The production is a parody tribute to the science fiction and horror B movies of the 1930s through to the early 1970s.
 Along with O'Brien, the film stars Tim Curry, Susan Sarandon, and Barry Bostwick and is narrated by Charles Gray with cast members from the original Royal Court Theatre, Roxy Theatre, and Belasco Theatre productions.
Shock Treatment was a TV film in 1995.
 The film was directed by Michael Schultz.
 It received one nomination for best visual effects in 1996 at the Gemini Awards.
Shock Treatment is a 1981 American black comedy musical film directed by Jim Sharman, and co-written by Sharman and Richard O'Brien.
 It is a follow-up to the 1975 film "The Rocky Horror Picture Show".
Blair Witch is a 2016 American found footage supernatural horror film directed by Adam Wingard and written by Simon Barrett.
 It is the third official film in the "Blair Witch" series and a direct sequel to the 1999 film "The Blair Witch Project", ignoring the events of its 2000 follow-up film "", given the events of that film being a film within a film.
 "Blair Witch" stars James Allen McCune, Callie Hernandez, Brandon Scott, Corbin Reid, Wes Robinson, and Valorie Curry.
 The film, shot in a found footage style, follows a group of college students and their local guides who venture into the Black Hills Forest in Maryland to uncover the mysteries surrounding the disappearance years ago of Heather Donahue, the sister of one of the characters.
 Initially, the film's connection to the "Blair Witch" franchise was kept secret, with the film having been shot under the fake title, "The Woods".
Part of the AFI 100 Years… series, AFI's 100 Years…100 Laughs is a list of the top 100 funniest movies in American cinema.
 A wide variety of comedies were nominated for the distinction that included slapstick comedy, action comedy, screwball comedy, romantic comedy, satire, black comedy, musical comedy, comedy of manners, and comedy of errors.
 The list was unveiled by the American Film Institute on June 13, 2000.
The Terror Factor is a 2007 American independent comedy horror film written and directed by Garry Medeiros and starring Matthew G. Hill, Nina Rusin, and John Sylvia.
 It premiered on October 30, 2007, and was completed on a US$2,000 budget.
 The film was voted "Best of New England" at the 2007 Rhode Island International Horror Film Festival and was later screened at the 2008 Fright Night and Rock & Shock Film Festivals.
 In 2010, it was released on DVD by Maxim Media International.
James David Sharman (born 12 March 1945), the son of boxing tent entrepreneur Jimmy Sharman, is an Australian director and writer for film and stage with more than 70 productions to his credit.
 He is renowned in Australia for his work as a theatre director from the 1960s to the present, and is best known internationally as the director of the 1973 theatrical hit "The Rocky Horror Show", its film adaptation "The Rocky Horror Picture Show" (1975) and the film's follow-up "Shock Treatment" (1981).
The Irony of Fate, or Enjoy Your Bath!
 (Russian: Ирония судьбы, или С лёгким паром!
, literally: The Irony of Fate, or With Light Steam ; trans.
 "Ironiya sudby, ili S lyogkim parom!")
 is a 1976 Soviet romantic comedy television film directed by Eldar Ryazanov.
 The screenplay was written by Emil Braginsky and Ryazanov, loosely based on the director's 1971 play, Once on New Year's Eve (Russian: Однажды в новогоднюю ночь ).
 The Irony of Fate was filmed in 1975 at the Mosfilm Studios.
 Doubling as a screwball comedy and a love story tinged with sadness, it is one of the most successful Soviet television productions and remains highly popular in modern Russia.
Jessica Harper (born October 10, 1949) is an American actress and producer, as well as a singer.
 Harper made her feature film debut in "Inserts" (1974), followed by a starring role in Brian De Palma's "Phantom of the Paradise" (1974).
 She played the lead role in Dario Argento's horror cult classic "Suspiria" (1977), for which she is best remembered.
 Her other films include "Stardust Memories" (1980), "Shock Treatment" (1981), "The Blue Iguana" (1988), "Safe" (1995), and "Minority Report" (2002).
 In addition to acting, Harper is also an author of children's music and books.