Aspects of pop culture people seem to misunderstand

[Nobody]

A few years ago I started a thread titled, Literary characters who come to symbolize the opposite of how they were portrayed.

I think that fits what the OP has in mind, so here are the two examples that were in my OP:

@Nobody

I never have read Uncle Tom, but I’ve always herd it used as a pejorative. So one day I looked it up on-line and was surprised to see

@Wikipedia

In the novel the Uncle Tom character is a black Christian martyr, morally superior to his white owners in an antebellum fiction whose subtext was an argument that the institution of slavery was immoral. Numerous adaptations altered the depiction substantially, often rendering him feeble, servile, or a race traitor. These adaptations, along with critical distaste for the original character’s passivity, contributed to the strongly negative connotations of the name in modern popular use.

Also, I never read about Little Lord Fauntleroy but have always heard the name in a negative connotation. So I was surprised to see

@Wikipedia

“Little Lord Fauntleroy” is now most often used as a term of derision. It describes a pompous spoiled brat, usually a young male, who takes his wealth and privilege for granted (while this is obviously not consistent with the original character, it is inspired by the perceived self-righteousness of the little lord, and an assumed odiousness in his overweening goodness).