an apple was involved but...
In the 17th century, Isaac Newton made a series of stunning discoveries about the universe, from mathematical equations that explained planetary rotation to investigations into light and prisms. But his best-known discovery was the theory of gravity. And his discovery did involve an apple, just not one falling on his head.
According to his biographer, William Stukeley, who interviewed Newton, the young scientist witnessed an apple fall from a tree as he "sat in a contemplative mood" in his family's garden. The story captured people's imagination, and at some point evolved from watching an apple fall to being hit in the head with the apple.