Ron Weasley’s “patronus” is a Jack Russell terrier. Moaning Myrtle’s full name is Myrtle Elizabeth Warren. Harry Potter’s uncle loves “Top Gear.” Fluffy the three-headed dog was repatriated to Greece. Tuition at Hogwarts is free.

With just a tweet, J.K. Rowling can change and shape the world of Harry Potter with new, authoritative information. And she has, quite a bit, in the years since concluding the story of the book and movie hero’s days at Hogwarts.

Once, Harry Potter’s biggest fans obsessed over every new word from Rowling, the details taking on an almost scriptural authority. But lately, that’s changed. Rowling remains a central, beloved figure among the Harry Potter series’ still-dedicated fan base. But she is no longer their distant, omniscient god.

“It’s obvious that people have this conflicted relationship,” said Andrew Slack, the co-founder of the Harry Potter Alliance and a fellow at Civic Hall Labs in New York. “But it has less to do with Jo and more to do with growing up.”

What’s changed? Slack turned to one of the most important lessons he learned from the Harry Potter books: “Our heroes are not what we think they are. They’re just like us.”

While the vast majority of Rowling’s readers have probably never ventured onto a “headcanon” Tumblr or bought a Wizard Rock album at LeakyCon, the core Harry Potter fandom has a presence on the Internet like no other. The huge fandom dragged fan fiction culture from the online fringes into the mainstream, as a generation of insatiable readers filled the gaps between Rowling’s books by reading and sharing their own stories, ranging from the creative and imaginative to that of, uh, questionable literary merit.

“The gap between ‘Goblet of Fire’ and ‘Order of the Phoenix,'” said Claudia Morales, who works for the Harry Potter Alliance, “was the longest and most torturous wait of the first wave. We all needed something to fill that time with, because our interest definitely wasn’t waning.”

Fans created news sites, encyclopedias and Harry Potter-influenced charities. They scoured every statement Rowling made for a hint at the next story and used those tiny details to write new ones. The “Deathly Hallows” publication day came and went, and readers considered what the future would be like now that the final story in the Harry Potter series was published, read and debated.

“There was a time after ‘Deathly Hallows’ came out — and a good deal of the time leading up to its release — where we thought there would never be more Harry Potter stories,” Morales said.

But Rowling didn’t stop.

On her Twitter account, on the encyclopedia-like Pottermore website, in a new play called “Harry Potter and the Cursed Child” and in the upcoming movie “Fantastic Beasts and Where to Find Them,” the official magical world of Harry Potter keeps expanding. Yet hardcore Potter fans have increasingly considered the possibility that Rowling’s vision for the world she created has diverged from the world that exists in their own imaginations. Given a choice, they might prefer their own.

Some have suggested that Rowling risks becoming the next George Lucas, a beloved figure who continues to amend and tweak the “Star Wars” universe he created, until fans can no longer stand it. And though Rowling has said that “The Cursed Child” is probably the end of new stories about Harry, the future of officially sanctioned content about the wider Potter world seems endless.

“The Cursed Child” was written by Jack Thorne, with the input of Rowling, and sanctioned as official canon. While commercially successful as a published script, the play has earned a mixed reception in the core fandom. The play deals with a grown-up Hermione, Ron and Harry and their children. It’s a topic that became fertile ground for fan fiction ever since Rowling wrote a vignette of her beloved characters’ adult lives in the epilogue of the final book.

“As someone who is a long-term member of fandom, it felt like I was reading a worse version of things I’d seen done for years,” said Sonja Petrovic, a fellow at the fan nonprofit group Imagine Better. “And that hurt to finally return to my favorite magical world and think that.”

Petrovic started reading the Harry Potter series before she was old enough to attend Hogwarts. She ran a Harry Potter club at high school. Online, she ran a Tumblr for sharing queer Harry Potter “headcanons” — fan-created ideas and stories that, while technically unofficial, reveal the importance of the actual canon to the writer.

Growing up, “I was literally the Harry Potter girl. Even some teachers called me this.” Petrovic said. “The people most often involved in the fandom, especially online, were other kids who didn’t quite fit in. And we all bonded over this beautiful story in which we saw ourselves and learned to love.”

When Petrovic picked up “The Cursed Child,” she found some things she liked: the story of Scorpius Malfoy, the son of Harry’s school rival, Draco Malfoy, and the play’s exploration of themes of loneliness, a common thread in the original books. But unlike with the original Harry Potter series, it was harder for Petrovic to relate to the version of Rowling’s world in “The Cursed Child.” Instead, she connected better to the fan-created stories.

“They have been explicitly queer. They’ve been more true to the original characters we fell in love with. They have dealt with issues of time travel better,” Petrovic said. “They have dealt with loneliness and isolation without being forceful about the situations that call for them. They were more nuanced and warm.”

The Harry Potter Alliance’s Morales explained why the fan versions appeal to her. “Because I grew up with wizard rock and fan fiction, I’ve never felt particularly beholden to the so-called sanctity of canon,” Morales said. Later, she confessed: “I still haven’t read past page 50 of ‘Cursed Child.’ This has never happened to me.”

Perhaps paradoxically, Morales, Petrovic and Slack said the values they learned from the original seven Harry Potter books helped them to grow beyond Rowling’s expanded vision for the franchise. All are activists involved with charitable organizations with direct connections to the fandom that work for change in the real world explicitly because of the moral lessons of Rowling’s work, they said.

“At the end of the day, I’m always going to be thankful to J.K. Rowling for creating this world, for teaching a generation of fans how to fight evil with love and guts and friends, for revolutionizing literature and revolutionizing fandom and revolutionizing me,” Morales said. “But to put canon on a pedestal and build fandom around canon alone is incongruent with Harry Potter’s messages. Everything about Harry Potter is different; its fandom is no exception.”

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