He is also known for his work in television, writing screenplays for such noted series as The Twilight Zone and Star Trek.
Born in a barn, he had to repeat the sixth grade and dropped out of school entirely in the eighth. He briefly served as a telegraph operator then draftsman in the Army, enrolled at now Auburn University under the G.I. Bill, quit to return to his travels around the U.S.A., working as an draftsman, before deciding he wanted to become a writer. In 1960 the first story Johnson ever wrote served as the basis for the Rat Pack movie Ocean's Eleven, although most of the details were changed for the film. He joined a circle of Southern California science-fiction writers that included William F. Nolan, Charles Beaumont, Richard Matheson and Ray Bradbury. Through them he met Rod Serling, to whom he sold his first story ("All of us Are Dying", produced as The Four of Us Are Dying) and, later, his first teleplay (A Penny for Your Thoughts).
His support for the legalization of marijuana is also well known.