After he married Sally and they moved away he like I mentioned, virtually ceased to exist and, by the next season, was never mentioned again. The difference between Mike and Chuck Cunningham, of course, was that Mike had been a major character. In some later episodes, when Steve mentions his three sons, he's referring to Robbie, Chip, and the adopted Ernie.

Similarly, in his first episode, Uncle Charlie, a character we had never met, shows up at the house one day to visit his brother Bub. Charlie was told that Bub had taken a trip to Ireland to visit family members. But we never heard about Bub again, and Charlie moved in permanently and took over Bub's housekeeping duties.

Mike was mentioned a few times in the sixth season, but there were even inconsistencies with those mentions. In the first episode of that season, Steve mentions Mike got a job "back east." In a later episode he's referred to as being in Arizona.

After that season he is never mentioned by name again; however, in a few references, he is "kinda" acknowledged as being the first son.

Similarly, Bub is mentioned here and there in the fifth season after his departure. In one I think I recall, Charley refers to him as Bub, which is supposedly a Douglas family grandfather reference Charley O'Casey would never use--he would call him Bill.

There is a difference, in that Mike was shown leaving to start his married life, while Chuck (to my knowledge) disappeared with no explanation whatsoever.

This whole thing seems to be a point of fascination and/or derision among casual watchers of the M3S series. Keep in mind that talking about having 4 sons, without Tim Considine ever making another appearance, would have just caused confusion for later viewers at the time who had never seen Mike.

Why this crap is STILL stirred up, over 50 years since the series ended, is beyond me. It's time to give it a rest. Too few people appreciate older music, TV, film, novels, etc. for the good aspects, they want to dig in and find fault, it becomes tiresome. This is just one of MANY thread topics at S.O. that finds fault with a series' producers/writers/actors, it just never ends. End of rant!

I think Chuck was retconned out of existence after a few early appearances. References were made by Howard and Marion, later, that would indicate Chuck didn't exist--that they had Richie and Joanie and that was it.

Not sure why the show runners would do that, but biff is right--that's been discussed to death--and so has Mike Douglas, and so have inconsistencies on Leave it to Beaver.

And an exploration of the Bewitched board would find tons of opinions the second Darrin, and ad nauseum discussions on whether or how Dick York and Elizabeth Montgomery got along.

Mike was mentioned a few times in the sixth season, but there were even inconsistencies with those mentions. In the first episode of that season, Steve mentions Mike got a job "back east." In a later episode he's referred to as being in Arizona.

After that season he is never mentioned by name again; however, in a few references, he is "kinda" acknowledged as being the first son.

Similarly, Bub is mentioned here and there in the fifth season after his departure. In one I think I recall, Charley refers to him as Bub, which is supposedly a Douglas family grandfather reference Charley O'Casey would never use--he would call him Bill.

Season 7's "Fly Away Home" (https://www.imdb.com/title/tt0655025/) is supposedly, the last time (https://forums.primetimer.com/topic/3400-my-three-sons-general-discussion/?do=findComment&comment=5364947) that Mike is mentioned in the series.

This thread reminded me of a scene that might be the last one where Mike was referenced but not by name. In S09 EO3, Robbie tells Steve he's not ready to be a father. Steve says he wasn't either until the nurse at the hospital showed him a "little, red, wrinkled squirming thing." That thing would have been Mike.

https://archive.org/details/my-three-sons-s-09-e-04-the-grandfathers/My+Three+Sons+++S09+++E03+++Life+Begins+In+Katie.mp4?start=369.9

Maybe they didn't mention him by name to avoid confusing viewers that never saw the older episodes.

Both Chuck's were on "together" on the Happy Days 30th reunion just shown on METV 12/28/25

Mrs C was so funny ....

Who was the first TV character to disappear without any explanation? (https://www.quora.com/Who-was-the-first-TV-character-to-disappear-without-any-explanation/answer/Rob-Morris-46)

One character who left with a full explanation was later made to vanish as though he never was. On My Three Sons (1960–1972), the original ‘male Nanny’ was the boys’ grandfather (Steve’s father-in-law) Bub O’Casey. He was played by sitcom legend and screen vet William Frawley, aka Fred Mertz. Well, one day Frawley’s studio physical means he can no longer be insured. It takes bringing in Lucy herself to get him to accept this. After a ruckus with his replacement William Demarest, he was even told to stop visiting the set. Depressed and in poor health, he died about eighteen months later. But that’s not where it ends. In episodes now removed from Uncle Charlie O’Casey’s intro, it begins to seem like Charlie was there even in flashbacks from episodes we know Bub was in. Eventually, it begins to seem like Charlie was always there. Then it accelerated. Ernie’s adoption was barely referred to at all, after time went by. Oldest son Mike and his bride stopped being mentioned at all a certain point, and it was again almost like Ernie had always been the third son by birth.

So even when you know what happened, it doesn’t stop them from vanishing.

The self-proclaimed "Classic TV Expert" who wrote that does not know that it was Charley, not "Charlie."

Our "expert" writes:

"In episodes now removed from Uncle Charlie O’Casey’s intro, it begins to seem like Charlie was there even in flashbacks from episodes we know Bub was in."

I'd like to see him give an example of that, because the very few flashbacks involved Steve and the boys (such as his talking to a very young Chip about marriage) -- there was no reason for Bub to appear in such a flashback nor was there any implied presence of Charley having been there.

Nothing "accelerated" -- the series simply moved on. Twelve (12) seasons! A new normal was established as time went on. Time to get over it...!

Ernie's adoption was "barely" referred to, but it WAS referred to. When Dodie is adopted (several years later, in season 10), Ernie says, clear as a bell, "I'm adopted."

By the way, as Biff mentions too, there are a few flashbacks during the story arc about Chip's and Polly's elopement. One time, Steve is talking to a young Chip about marriage ("I haven't even got my driver's license yet!") while he's going to bed; in another scene, he and Chip are washing dishes and are talking about a girl, Doreen, who's making "goof eyes" at Chip. Both scenes are likely from the first season, and have nothing to do with Bub.

I'm guessing that the infamous "McMurray method" production technique was one solid reason for why Mike and Sally's actors, Tim Considine and Meredith MacRae, because things had to be planned out way in advanced. Also, by this point, Meredith MacRae was able to land another job with Petticoat Junction, so it wasn't like she actually "needed" My Three Sons by that point anyway.