Question: Clive Barker and Frank Pierson share what occupation?

Context paragraphs:
The Hellbound Heart: The Hellbound Heart is a horror novella by Clive Barker, first published in November 1986 by Dark Harvest in the third volume of their "Night Visions" anthology series, and notable for becoming the basis for the 1987 movie "Hellraiser" and its franchise.  It was re-released as a stand-alone title by HarperCollins in 1988, after the success of the movie, along with an audiobook recorded by Clive Barker and published by Simon & Schuster Audioworks.  It retains the gory, visceral style that Barker introduced in his series of collected short stories "The Books of Blood".  The story focuses on a mystical puzzle box and the horror it wreaks on a family that is unfortunate enough to come across it.

Butterball Cenobite: Butterball is a character from Clive Barker's "Hellraiser" franchise.  He is a Cenobite, one of a group of extradimensional beings who experiment in forms of extreme sadomasochism as part of a religious devotion to hedonism.  He is also one of the first Cenobites introduced in the franchise, appearing both in the initial novella, "The Hellbound Heart", as well as the films "Hellraiser" and "".  Butterball also made an appearance in Clive Barker's comic book sequel to "Hellbound," the "Hellraiser" comic book series published by BOOM!  comics in 2011.  Despite appearing to be the second-in-command of the Cenobites in "The Hellbound Heart", in the film and comics he primarily functions as a member of Pinhead's entourage.

Clive Barker, Illustrator: Clive Barker, Illustrator is a book of ink sketches and some full-color paintings by British author Clive Barker.  It was published in 1990 by Arcane/Eclipse Books.  It also contains a lengthy interview with Barker, in which he talks about the various aspects of his work.  As with his fiction, his artwork is concerned with mythology, monstrous figures, the grotesque, human sexuality, and secret identities.  He also discusses his influences, which range from Jean Cocteau, Goya and William Blake to various Disney movies.

Frank Pierson: Frank Romer Pierson (May 12, 1925 – July 22, 2012) was an American screenwriter and film director.

Clive Barker's Undying: Clive Barker's Undying is a first-person shooter survival horror video game developed by EA Los Angeles and published by EA Games.  Noted horror author, the titular Clive Barker, was consulted in shaping the game's plot and background lore and also provided the voice of Ambrose Covenant, a character in the game.

Tortured Souls: Tortured Souls, also known as "Clive Barker's Tortured Souls", is a series of six action figures and a starring the characters of the series.  Distributed by McFarlane Toys in July 2001, the series included six monsters designed by horror author Clive Barker.

Saint Sinner (film): Saint Sinner (full title Clive Barker Presents Saint Sinner) is a 2002 horror TV-movie written by Doris Egan and Hans Rodionoff based on a short story by executive producer Clive Barker.  It was directed by Joshua Butler.  Aside from the title, it is unrelated to the comic-book series published by Marvel Comics' Razorline imprint and created by Barker.  In this movie, an immortal monk hunts down two succubi.  It premiered on the U.S. Sci Fi Channel on October 26, 2002.

Clive Barker: Clive Barker (born 5 October 1952) is an English writer, film director, and visual artist.  Barker came to prominence in the mid-1980s with a series of short stories, the "Books of Blood", which established him as a leading horror writer.  He has since written many novels and other works, and his fiction has been adapted into films, notably the "Hellraiser" and "Candyman" series.  He was the Executive Producer of the film "Gods and Monsters".

Clive Barker's A-Z of Horror: Clive Barker's A-Z of Horror was a documentary series first broadcast on BBC2 in 1997.  It was written and hosted by Clive Barker and explored the history of horror, from the cinema to art.  A tie-in book was released featuring art work by Barker and film reviews by Stephen Jones.

Clive Barker's Jericho: Clive Barker's Jericho, sometimes referred to as simply Jericho, is a first person shooter survival horror video game with author Clive Barker providing the premise of the storyline.  The game was released for Microsoft Windows, PlayStation 3 and Xbox 360 in 2007.

Supporting paragraphs: Clive Barker Frank Pierson
Answer: film director