These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Mr. Slate is frequently presented as an expy of Mr. Spacely, but there's plenty of evidence that he's simply a no-nonsense but well-meaning employer. On at least one occasion, when an accounting error led to Fred not getting a bonus, he came to Fred's house in person to apologize.
He does have his Jerk Ass moments, most notably the episode where it's revealed he and his son have an entire routine set up to prevents his employees from asking for raises (involving making it look like the son had done the same and Slate was firing him only to rehire him at a paycut after much grovelling)... and doing this to Fred despite knowing he has a baby on the way.
Family-Unfriendly Aesop: Though by no means a "family friendly" commercial due to alcohol, this commercial seems to promote getting people good and drunk to get them to do whatever you want.
"Funny Aneurysm" Moment: The infamous cigarette ad becomes this when you realise that Jean Vanderpyl, (Wilma's original voice actress) died of lung cancer in 1999. The commercial even shows Fred lighting up a cigarette for Wilma, before lighting one up himself.
The show and its live-action movies were very popular in Quebec.
The cartoon's localized version was also a major hit in Hungary, as the entire dialog had been rendered in witty rhymes by a famous poet. Due to the dub's success, some later dubs of cartoons and comedy movies used the same tactic. The show's later seasons and the spin-offs aren't that well known, though.
Seasonal Rot: Some have noted that after Pebbles was born, the show shifted its tone to be a bit more child friendly, and consider it to have dropped in quality as a result. While this viewpoint isn't universally accepted among fans, a way more common viewpoint is that the show's quality took a major drop when the Great Gazoo showed up.
There are also quite a few jokes sprinkled throughout the series that would, today, be seen as sexist or misogynistic.
What Do You Mean, It's Not for Kids?: The series was a primetime sitcom that was never geared towards only children, as most of the situations and jokes were way over the heads of most kids at the time (and now). Later merchandise and spinoffs decided to go against that mindset, however.
Hence the sponsorship by Winston's Cigarettes, and Busch's Beer.
The Woobie: A meta-example. When it came to merchandise, Betty always seemed to get the short end of the stick, having notably been left out of the Flintstones Vitamin assortment, and even being upstaged by the Sabre Toothed Tiger from the end credits for a Push Pop flavour (which was, to add insult to injury, blueberry flavoured.) Apparently, enough people complained about this, as Betty finally got her own Vitamin in 1995, twenty years after that fact. There is even an FAQ on the official website, the last question asking about her presence in the Vitamin lineup.