As a Writer, Shull wrote the 1960 play Fenton's Folly, which was adapted as Fentons völlig verrückte Erfindung (1967), an independent German movie filmed in Austria. Shull also wrote the story for the 1966 thriller movie Aroused, and co-authored, with william L. Rose, the dramatic film Pamela, Pamela You are... (1968).
He got his first big break as an actor when he was cast in Minnie's Boys in 1970. Additional theatre credits include Goodtime Charley (in which he sang a duet "Merci, Bon Dieu"; and for which he received Tony and Drama Desk Award nominations), Fools, The Front Page, A Flea in Her Ear, and Victor/Victoria.
Shull's screen credits include thirty movies, The Anderson Tapes (1971), Klute (1971), Slither (1973), The Fortune (1975), Splash (1984), Garbo Talks (1984), Unfaithfully Yours (1984), Housesitter (1992) and Private Parts (1997).
His television appearances included Love, American Style in episode "Love and the Locksmith", Ironside "Once More for Joey" aired 1974, Good Times "The Visitor", The Rockford Files "The Great Blue Lake", Alice "Flo's Chili Reception", Diana co star, Lou Grant episode "Samaratan", Hart to Hart, and Holmes & Yo-Yo starred as a police detective, as well as numerous television movies. He also appeared as the judge in an MTV music video, "Keeping the Faith" (1984), by Billy Joel. In 1963 Richard became a member of the historical theater club, The Lambs, served on its council and remained a member until his death.
In 1995, Shull co-founded the North American Araucanian Royalist Society (NAARS) with Daniel Paul Morrison. The NAARS studies the Kingdom of Araucania and Patagonia which was founded in 1860 by the Mapuche people of South America. The NAARS devoted a large portion of issue number 10 of their official journal, The Steel Crown, to the life of Shull.
In a 2012 interview, Shull's Holmes & Yo-Yo co-star John Schuck remembered him as "a very funny actor and a unique man," adding that Shull "lived in the ’40s. He bought ’40s clothing, he only used pen and ink, he had his own railroad car which he would attach to trains and travel around the country. He had a 1949 Chevrolet car. I mean, he truly lived in the past. Quite remarkable."
