My favourite is the story that there was mass panic over a radio broadcast of War of the Worlds where everyone thought a real alien invasion was happening. I heard this story as a kid and really thought this was a cruel prank played by the radio station.
In reality, they made it clear at the beginning of the broadcast, and twice during, that it was fictional. Not that many people were listening and most of the people who were, were aware it wasn’t real. A few idiots freaked out and it somehow turned into a story of mass panic. It was propaganda by newspapers to discredit radio.
Oh, I’ve got a carrots one, too. Rabbits don’t have a particular fondness for carrots. We just think they do because of Bugs Bunny. But Bugs eats carrots to imitate a Clark Gable scene in It Happened One Night, with the carrot substituting for a cigar. Over time the connection got lost and it just sort of became “rabbits = carrots”.
They don’t mind them, but they have no particular preference for them.
That’s not the only Bugs Bunny-related thing, either. “Nimrod” has come to mean “idiot” because of its use by Bugs. But that’s not the intended meaning in the cartoons. He specifically says it to Elmer Fudd. Nimrod is a Biblical figure, known for being a great hunter. He’s being sarcastic. But again the reference got lost and people just thought it meant “idiot”.