Roger Ewing (born January 12, 1942) is a former actor originally from Los Angeles, California. He is best remembered for his characterization of part-time deputy marshal Clayton Thaddeus "Thad" Greenwood in thirty-six episodes (October 2, 1965 - September 25, 1967) of the long-running CBS western television series Gunsmoke with James Arness. Among Ewing's last Gunsmoke appearances were on episodes entitled "The Prodigal", "Nitro" (Parts 1 and 2), "Ladies from St. Louis" and "Mistaken Identity". Before he was cast as Thad, Ewing appeared on Gunsmoke once in the role of Ben Lukens in the episode "Song for Dying", which aired on February 13, 1965. Ewing's first television appearance was in 1964 as Marvin Grogan on ABC's sitcom Bewitched (Elizabeth Montgomery) in the episode entitled "The Girl Reporter".