William is well-versed for playing villainous roles, and is perhaps best known for his recurring role as J.R. Ewing's arch nemesis Jeremy Wendell on the classic television series Dallas, primarily from 1984 through 1989. Prior to this, Smithers had brief stints on such popular TV shows as Young Dr. Malone (from 1962 through 1963) and Peyton Place (1965 through 1966). He was also a regular on the short-lived 1976 series Executive Suite. He also appeared in the 1980 made-for-TV movie The Return of Frank Cannon, which co-starred Diana Muldaur.