(written from a Production point of view)
Clark filmed his scenes as the Gorn on Wednesday 9 November 1966 and Thursday 10 November 1966 at Vasquez Rocks. He filmed his scene for "The Return of the Archons" on Wednesday 7 December 1966 at the 40 Acres backlot, and his scene for "Mirror, Mirror" on Wednesday 2 August 1967 at Desilu Stage 9.
38 years after introducing the race in "Arena", Clark, as a guest of stunt coordinator Vince Deadrick, Jr. (whose father had been a fellow TOS stuntman) visited the set of ENT: "In a Mirror, Darkly, Part II" during the shooting of the scenes in which the Gorn made their first live-action appearance since that episode.
In 2009 he appeared in the British television documentary Bring Back Star Trek in which he reprised his role as the Gorn Captain with show host Justin Lee Collins standing into William Shatner's place in a parody of the famous scene in "Arena".
In 2014 he made a guest appearance as the mirror universe Halkan administrator Tharn in Star Trek Continues E03 Fairest of them All.