How do they make Uncle Martin dis/appear?

In some scenes Uncle Martin will raise his antenna and then disappear from beside Tim. It looks like the same effect used in "Bewitched." It's really smooth and when playing frame by frame it can be seen that sometimes the effect is done with amazing precision. Other times there is a slight jump.

How do they do it?

My guess is that they play the scene, and at the point where Martin will dis/appear the actors freeze in place as best they can. The director calls "CUT/RESET" whereupon Walston walks in/out of the scene as quickly as possible so that the Bixby moves as little as possible. The director calls "ACTION" and the scene resumes. In the editing room the film between "CUT" & "ACTION" is cut out and the film is spliced there and that's it. I'm pretty sure that's basically how it's done. The only thing is that sometimes the characters fade in/out giving an extra smoothness. To do that, it seems that the last few frames before the edit and the first few frames after the edit are progressively developed so that they gradually go from clear to fully developed (or vice versa) and then the edit is overlayed by however many frames.

I suspect there is more to the effect than the simply procedure I have outlined. I remember one scene in Bewitched where a character appears while another character is walking. The appearance is done in midstep. It would not appear to have been possible for the character to freeze when walking, so it seems that they shot the scene twice, reproducing the walk step for step with the arms in the same position, etc. Wow that's amazing.