I don't know for sure... it could be any number or combination of memory biases.
I just found this Snopes article discussing The Mandela Effect (the phenomenon of collective groups misremembering the same information from history) in reference to The Berenstain Bears books. It just blew my mind because I would have BET MY LIFE the books featured the BerenSTEIN Bears and not the BerenSTAIN Bears.
http://www.snopes.com/2016/07/24/the-mandela-effect/
I am legitimately dumbfounded right now.
Well, that's just because Berenstein sounds like a name. Almost no one knows that Wedgwood China is spelled with only one E. Almost no one, but if you have a piece, turn it over, there's only one E. Also, Sherbet only has one R. Tons of people think it's sherbert.