He also co-wrote the screenplay along with director Jim Sharman for the film adaptation, The Rocky Horror Picture Show (1975), and appeared on-screen as Riff Raff.

His other acting credits include Flash Gordon (1980), Robin of Sherwood (1985), Spice World (1997), Ever After (1998), Dungeons & Dragons (2000), and Elvira's Haunted Hills (2001).

After a long and successful career based in the United Kingdom, O'Brien gained dual citizenship with New Zealand in 2011, where he resided in Tauranga.

[12] In the summer of 1972, he met director Jim Sharman who cast him as an Apostle and Leper in the London production of Jesus Christ Superstar.

Sharman then cast O'Brien as Willie, the alien in his March 1973 production of Sam Shepard's The Unseen Hand at the Royal Court Theatre Upstairs.

Sharman suggested changing the working title from They Came from Denton High, and The Rocky Horror Show opened at the Theatre Upstairs in June 1973.

After seeing the second night's performance of The Rocky Horror Show in the Theatre Upstairs, Jonathan King produced the original cast soundtrack in just over 48 hours during an off-stage weekend, and rushed it out on his UK Records label.

[17] O'Brien continued writing musicals with arranger Richard Hartley, including: T. Zee (1976), Disaster (1978), The Stripper (1982 – based on the Carter Brown novel and produced in Australia), and Top People (1984).

[18] O'Brien became the presenter of UK Channel 4's game show The Crystal Maze in 1990,[19] specialising in sardonic put-downs, occasional eccentricities and playing his harmonica at random intervals.

In 1995, he performed a select number of shows as the devilish charmer Mephistopheles Smith in a musical/comedy show he wrote entitled Disgracefully Yours, to which he later gave permission to be adapted into a musical, first by Eubank Productions for the Kansas City Fringe Fest in 2006, and more recently by Janus Theatre Company for the Edinburgh Fringe 2007, simply entitled Mephistopheles Smith.

[citation needed] A script for another rumoured sequel entitled Revenge of the Old Queen of Rocky Horror, has been circulated on the web and reproduced on various fan sites, although it has been officially denied as O'Brien's work by his representatives.

He wrote the lyrics for The Stripper (based on the book by Carter Brown), a musical which had its British premiere at the Queen's Theatre, Hornchurch (London) on 28 August 2009.

[23] In 2004, members of the Hamilton City Council in New Zealand honoured O'Brien's contribution to the arts with a statue of Riff Raff, the character he played in The Rocky Horror Show, on the site of the former Embassy Cinema.

Also in December, he visited Hamilton, New Zealand, for An Evening With Richard O'Brien, with presenter Mark Sainsbury and director Fiona Jackson.

[25] In December 2008, O'Brien donated his original script Pig in Boots to the Wireless Theatre Company,[26] who converted it into an audio pantomime.

[27] In March 2012, he gave a performance of song and autobiographical stories, It's Party Time with Richard O'Brien at the Hamilton Founders Theatre to celebrate his 70th birthday.

[34] In a 2020 interview with The Guardian, O'Brien was reported as stating: "I think anybody who decides to take the huge step with a sex change deserves encouragement and a thumbs-up.