(written from a Production point of view)
Fix is one of only two Star Trek actors verified as a veteran of the First World War (the other being Ian Wolfe), where he served in the US Navy. He was born earlier in the 20th century than any other Star Trek actor.
Following the Navy, Fix became an incredibly busy character actor who got his start in local productions around his New York home. By the 20s he had moved to Hollywood and performed in the first of almost 350 movie and television appearances. In the 30s, he became friends with John Wayne, coaching him in acting, and eventually appearing in about twenty-five of his films. Many of his early characters were scoundrels of one sort or the other; as he matured, he took on more benevolent, avuncular roles (such as Doctor Piper). He is most well known as Micah Torrence from the ABC series The Rifleman, appearing for the show's entire run. Bill Quinn, who played the father of Piper's successor, Doctor Leonard McCoy, in the fifth Trek film was a semi-regular on that series. One Rifleman episode, entitled "Three Legged Terror", featured not only Fix and Quinn, but also John Hoyt, the man who played Piper's predecessor, Doctor Phillip Boyce, in the first Trek pilot.
Other television credits included The Adventures of Superman (1953-1954, with Anthony Caruso, Joseph Mell, and Elisha Cook, Jr.), recurring appearances as District Attorney Hale on Perry Mason (1957-1963), The Twilight Zone (1964), The F.B.I. (1965-1973, with Marj Dusay, Clint Howard, Steve Ihnat, Paul Carr and series-regular Stephen Brooks), The Time Tunnel (1966, with James Darren, Whit Bissell, Lee Meriwether and Paul Carr), Voyage to the Bottom of the Sea (1966), The Wild Wild West (1966-1967, with Sarah Marshall, Michael Dunn and Anthony Caruso), Owen Marshall: Counselor at Law (1971, with DeForest Kelley) and Mannix (1972, with Rex Holman and Byron Morrow). He appeared in the Battlestar Galactica episode "Take the Celestra" as Commander Kronus (1979). He again appeared with DeForest Kelley in the movie Night of the Lepus (1972). In 1970 he had a smaller role in Michelangelo Antonioni's counter-culture film, Zabriskie Point, which also featured Lee Duncan.
On film, Fix was as prolific. Fix was cast as Judge Taylor in the 1962 classic legal drama To Kill a Mockingbird, co-starring Charles Dierkop, Richard Hale, John Megna, Frank Overton, Brock Peters and William Windom.
Fix died in Los Angeles, California, as a result of kidney failure.
Samuel A. Peeples, the writer of "Where No Man Has Gone Before", thought very highly of Paul Fix. In a 1988 interview, Peeples commented, "I knew Paul for many years, and he appeared in some of the shows I did [....] In my opinion [...] [he was] a splendid actor." (The Star Trek Interview Book, p. 118)