I remember being confused about The Flintstones thing as a kid. In my head I always pictured it as it is now, but what confused me was when I actually payed attention and spelled it out. It was The Flinstones and I could not wrap my head around it. It didn't make sense at all.
On another note I used to watch The Lord of the Rings trilogy monthly, I had the entire thing memorized and it was definitely "Run, you fools".
Yeah the Flintstones is just one of those things that's hard to pronounced correctly because of the 2 'T's so people just got lazy with it. Then we remember it being a different way in retrospect. Pretty much all of these have rational explanations and I myself have never had that great of a memory.
The first Mandela Effect that actually freaked me out was Mona Lisa having a veil over her head. How come I never noticed it? Now it's suddenly everywhere and apparently always has been. That's when I started to take this phenomenon seriously.