Yabba Dabba Doo!

Everyone over a certain age knows and loves the Flintstones - but does everyone call Fred, Wilma, Barney and the gang "The Flintstones" or "The Flinstones" with a missing "t"? Those experiencing the Mass Memory Discrepancy Effect see the latter.

There is always the danger of a straightforward misreading of these type of situations. There's a clear reason for the spelling with the "t" included in this case - the show is about cavemen, who used flint stones. Those who didn't make that connection might also have not paid attention to the actual spelling, and so only think something is different now they actually concentrate on it.

Various reports vary from those who "definitley" remember it without the "t" to those who claim it has switched back and forwards between the two. 

Many reports before the Mandela Effect

There's a lot of buzz around this one on the internet, plenty of which goes back way before the Mandela Effect became popular from 2012 onwards. The focus seems to be around the prononciation of Flintstones  as one or two words. If the accent, or dialect spoken, naturally separates it into two distinct words, such as British Englsih, then people tend to remeber the "T" more, whereas when it's a variation where iuts more natural to say it as one whoel word, as in spoken US English, it tends to be people who drop the "T". This observations doesn't hold fast and true or it would have been spotted before, but since this Mandela Effect came up, it's had such widespread exposure that this pattern was observed.