(written from a Production point of view)
In early-October 1964, Gene Roddenberry wanted Robert Justman to become the associate producer on "The Cage", the first pilot episode of Roddenberry's original Star Trek. However, Justman rejected the offer, fearing he did not have enough post-production knowledge which such a show might demand. In his stead Justman recommended his friend, Byron Haskin for the work, not knowing that Roddenberry already contacted Haskin, who eventually got the job. Yet, Haskin reciprocated the favor of his friend by insisting Justman to be hired as the assistant director for the same project, a suggestion eventually followed up by studio executive Herb Solow, becoming Haskin's successor afterwards. According to Justman, he and Roddenberry didn't get along well, explaining why Haskin was not in Star Trek beyond the original pilot.  Haskin conceived Roddenberry as "probably another rank amateur, who doesn't know diddley and wants me to save his ass". Furthermore, Justman adds that Haskin always argued with Roddenberry on the special effects. He frequently pointed out that Roddenberry's ideas were unfeasible, but Roddenberry pushed him to stick to them, which led to frequent arguments. (Inside Star Trek: The Real Story, pp. 29-31, 34).
His work on "The Cage" went uncredited on-screen, but was later, as archive footage, seen in "The Menagerie, Part I" and "The Menagerie, Part II", and he did receive on-screen credit on the latter episode.
Having worked worked in the motion picture and television industry from the early 1920s through the late 1960s, Byron Haskin started out as a newspaper cartoonist, then became a commercial-industrial and newsreel cinematographer in the 1920s. He soon turned to special effects (as visual effects were still called in that time, the distinction between the two only introduced decades later) photography, and worked in Hollywood as a visual effects designer for nearly twenty years. His work as visual effects artist was widely recognized at the time as it had earned Haskin one technical Academy Award in 1939, supplemented with four co-nominations in 1940 (for The Private Lives of Elizabeth and Essex), 1941 (for The Sea Hawk), 1942 (for The Sea Wolf), and 1943 (for Desperate Journey), all of those shared with Sound Editor Nathan Levinson. Haskin's reasons for his later arguing with Roddenberry, who had no experience with these whatsoever, over the effects for "The Cage", were therefore more than founded.
Later he went on to direct mostly science fiction and fantasy films (often in collaboration with legendary producer/director George Pal), including such classics as, most conspicuously, The War of the Worlds (1953, co-winning him a 1954 Hugo Award), The Naked Jungle (1954, with Abraham Sofaer), Conquest of Space (1955) and From the Earth to the Moon (1958). In the late-1940s, and early-1950s he also directed several Walt Disney productions, including the classic Tresure Island (1949). Between 1963 and 1964 he directed six episodes of The Outer Limits, including "Demon with a Glass Hand", with Arlene Martel and Abraham Sofaer, written by Harlan Ellison. A none-science fiction and fantasy film Haskin directed, was the 1951 western Silver City, where he met and befriended Art Director Franz Bachelin, who he brought in on "The Cage" in October 1964 as replacement for the suddenly departed Pato Guzman. (These Are the Voyages: TOS Season One, 1st ed, p. 44)