The vigorous calisthenics routines on the parallel bars etc. apparently performed by Uncle Martin in this episode, were actually done by Bill Blackburn, who was Ray Walston's stand-in on the show, and was also a talented gymnast. (This is why all of the athletic routines that do not show Walston in a close-up were shot from behind.) Later in the episode, as Martin is preparing to enter the spaceship, one of the people with whom he shakes hands is Bill Blackburn.