AEC1990 is in no way associated with JK Rowling, Warner Brothers, or any other owner of the Harry Potter franchise.
The Story of how Muggles Came to Know Quidditch
And then one day, Harry Potter died.
Forty-nine days later, a child was conceived and then promptly aborted by magical means. The baby's soul, however, had been anxiously awaiting its next great adventure and had not been ready to release its hold on its newly forming life and move on again to the next. Having only recently been relocated, not given enough time to recognize its new form as his own, the soul still carried the magic of its former identity and slowly began to remember the last life it had truly lived, and after long years of restless wandering, the ghost the soul became for want of life ceased to be the ghost of a quickly aborted child.
And that was how Harry Potter became a ghost.
At first, once the soul had finally, fully, reclaimed its identity as Harry Potter, the ghost was at a loss. He distinctly remembered being ready to move on; he had no reason to remain as an echo among the living. However, upon finding himself, for want of something familiar, returned to Hogwarts, he found that he was different from other ghosts. None of the school's staff or students could see him or interact with him as they could with the other ghosts, and though it took him a while to realize, the other ghosts did not realize he was there either.
So the ghost of Harry Potter began to wander.
He did not particularly want to be constantly reminded that, even to those who were only half there, he did not actively exist, so he took to large towns and cities. He wandered the busiest places, observing people, observing life. He watched society grow and change. He saw vast changes over short periods of time, and he occasionally noticed different stages of more subtle changes, changes that would last long periods of time. He wandered these places because it didn't feel strange to go unnoticed. After all, had he been alive, these muggles around him still wouldn't have paid attention to his presence.
Then one day, someone did.
She was a young, aspiring author, and to her, he appeared to only be eleven. They were on a train from Manchester to London, and she had wanted to make sure he wasn't lost or on the train by accident. She had even asked if his parents knew where he was. After so long of being unrecognized, unnoticed, he found this new interaction to be in pleasant contrast to his years of solitary wandering, and when she finally realized he was insubstantial, he was surprised that she immediately thought him some kind of muse. He never tried to tell her anything different, and when she asked him about himself, he responded with his stories. He followed her for some time, and eventually she began putting his stories down in ink. Every time he shared a story or she wrote a little bit more about him, he felt as if a weight he had never noticed had been lifted from his shoulders, and eventually, his story came to an end. The young author, now a young mother as well, hadn't quite finished penning his story, but he felt confident in her ability, and she no longer seemed to need him at her back, giving her more details, fleshing out the story.
So Harry Potter, once again, moved on.
Eventually, the young author finished the story of Harry Potter, and the story became wildly popular. It became so popular, in fact, that most muggles knew the name of the Boy Who Lived, and his story became the basis for a large franchise. At some point, the muggles had even devised a way to play Quidditch with out flying brooms and magical balls, and the sport became popular. However, by some means, the wizarding world never caught wind of the Harry Potter franchise, and before long, a batch of muggle-born students recently accepted to Hogwarts were standing before their flying instructor, stars in their eyes, asking if they were really going to learn how to play real Quidditch.
And this very much confused the flying instructor.
A couple weeks back I saw signs hanging up around my campus inviting people to come play Quidditch. At the time I wasn't quite sure what was going on there. Y'know, "Quidditch? How exactly?" I didn't go because I'm not one for sports, but yesterday I read an article in the school's newspaper about the sport. It was just and interview with one of the conveners, but it did clear up some of the "how exactly" question and implied that other college campuses also have Quidditch teams, and then today, this idea just kinda popped into my head during lunch, and I just wrote it.