In my recent Bob Bolling profile, I noted that he tended to change the designs of the characters depending on what kind of story he was doing. There's another reason why cartoonists change a character's design, of course: because the character hasn't appeared often enough to have a fixed design. One character who fit into both categories for Mr. Bolling was the never-named (at least in his stories) Mrs. Cooper. The look of Bolling's Mr. Cooper, while not entirely consistent, at least portrayed him as more or less the same guy every time: a middle-aged guy with glasses. (If you try to put these stories into some kind of strict continuity you would conclude that he actually got younger by the time his youngest daughter was a teenager.) But Mrs. Cooper? I don't have an example of her early appearances in this title, but all the women in the first few years looked the same: generic suburban housewives. (Except Mrs. Andrews who was "generic hot suburban housewife.")
But then Bolling introduced an older brother, Chic Cooper, and he realized that if Mrs. Cooper had a college-age son, she couldn't be as young as the other mothers in town. So in issue # 12 she became a pudgy middle-aged woman (like what poor Mary Andrews is destined to become).
Then, three issues later, Bolling decided to do some solo stories for Little Betty, and suddenly her mom looks not only younger than Mrs. Andrews, but younger than most teenagers in this universe. The implications of her being married to Mr. Cooper are frankly disturbing.
But in the very next issue, Mrs. Cooper puts in an appearance in one of the adventure stories. Bolling's technique for the adventure/mystery stories was to draw the kids in the normal, cartoony fashion but draw everyone else, including the parents, realistically. And so Mrs. Cooper goes from what we saw above, to what we see below:
Addendum: Here's another panel from the same story that shows the cartoony kids/realistic adults style Bolling used for these adventure tales.
But don't worry, in the very next issue she's back to being a cute cartoony blonde married to a man apparently half again as old as she is (still an improvement over twice as old, which is how he looked two issues ago).
A couple of years went by and Bolling introduced Polly, featuring her in four or five stories. Because the design for Polly was basically the same as the design he'd used for Mrs. Cooper in some of the earlier stories, Mrs. Cooper once again has to look like somebody who could have an older kid... but Bolling may have overdone it:
One issue later, Mrs. Cooper is back in a more plausible and moderately age-appropriate version.
But that wasn't the end of it, because when Bolling returned to the series in the '80s, Mrs. Cooper was once again looking like someone who should not be married to a schlumpy-looking guy (one who appears to spend most of his time chasing his daughter's cat across rooftops).
The lesson of all this? I'm not sure. Unless it's that Mr. Cooper keeps divorcing and/or disposing of wives in much the way that Mrs. Andrews keeps getting new and different-looking husbands. And even if he is a sort of modern Bluebeard, it wouldn't explain why his wives vary so greatly in age. One of those eternal comics mysteries, I guess.