The claim
“A falling apple inspired Newton's theory of gravity”
Disputed
Newton told the story himself, but the apple hitting his head is a later invention.
What's really going on
This one is half true. Newton often said watching an apple fall got him thinking about gravity, and people who knew him confirmed he told the story. Some historians still doubt it, and the apple that bonked him on the head is made up.
The receipts
“Newton often told the story that he was inspired to formulate his theory of gravitation by watching the fall of an apple from a tree.”
“Although some question the veracity of the apple story, acquaintances of Newton attribute the story to Newton himself, though not the apocryphal version that the apple actually hit Newton's head.”
More myths
Myth“Bulls charge because they hate the color red”Bulls are dichromatic, a kind of color blindness, so the red of the cape is irrelevant to them. Myth“Goldfish have a three-second memory”Goldfish remember things for months, not seconds. Disputed“The Great Wall of China is visible from space with the naked eye”Not the way the legend says. It's too narrow and blends into the land, and astronauts disagree about whether they've seen it.