Excellent guesses, but no.
It was this beast here, which Endora stole and gave to Darrin as a present:
The Reactor (show rod) - Wikipedia.
DARRIN: This makes the Batmobile look like a skateboard!
Ooh ooh, I think I might know…
Darn, late to the party. I was going to suggest ‘Robbie the Robot’, which was ubiquitous in TV shows and movies of that era. I’m pretty sure I even remember an episode of Columbo where Robbie appeared. Hey, my answer might be right too! 
I was gonna say the ‘UFO’ thingy that was everywhere. You know round and with a bump out on top.
I’m pretty sure it was on Batman.
I know it was on Bewitched.
I was maybe gonna say Michael Ansara…
actually, the most unrealistic thing to me is the protesting about using magic I mean ok lines would have to be drawn but for things like housework and mundane tasks? come on …
If it’d been I Dream of Jeannie rather than Bewitched…
(Ansara was married to Barbara Eden, and appeared in several episodes of IDoJ.)
Well, sure; but did that stop him from putting in an appearance on Bewitched as well?
Just popped in here to claim that my trust issues stem from pre-school, when the adults switched Darrins on us.
With no explanation, yet.
I saw, I think on twitter, a pic of Samantha with O.J. it said, the third Darrin was the worst.!
I’m always surprised that so many different central characters were each played by 2 different actors. (Darrin, Gladys Kravitz, Tabitha, Adam, Louise Tate, maybe more?)
Darrin’s father was played by two different actors as well.
Several actors including Alice Ghostly, Bernard Fox, and Paul Lynde played two different characters which included one re-occuring character (Esmeralda, Dr Bombay, Uncle Arthur)
Samantha had a cousin Serena she played, also.
I watched those reruns a lot as a kid, but I was an adult before I learned any of the roles (even Darrin) were recast. I think it might be because Bewitched (1964-1972), like a lot of the other reruns I watched, spanned several swift fashion and hair fads in America.
I’m amazed how many episodes per season they had.
No self-respecting sitcom star would put up with that crap these days.
Running a re-run of a show during the season wasn’t done as commonly then as it is now, which is why they were making 30+ new episodes a year. The norm was that you ran a new episode most weeks from September though the late spring, though there might be weeks when the show was pre-empted for holiday specials, etc.
Then, during the summer months (when viewership was generally lower anyway), the networks would run “summer replacement” show in the main show’s time slot, before the primary show returned with new episodes in the fall.
I noticed there’s a few thinking back episodes too.
There’s an industry term for that: “clip show.” It’s a way to save money, and sometimes to get something ready for air when the show is behind on its production timeline.
I figured Elizabeth Montgomery might have been on her real maternity leave. I guess she really had a baby. She looked thick for many eps before they announced Sam’s pregnancy.