Harry Potter’s sprawling, magical universe is one so ubiquitous it’s easy to imagine that all of us have had some brush with it, whether that’s reading the books, watching the movies, or just catching glimpses of the cultural phenomenon left in the wake of the publication of J.K. Rowling’s Harry Potter and the Philosopher’s Stone 20 years ago this summer. It’s not just an English-speaking phenomenon, either: shown in dozens of countries and translated into over 70 languages, the Harry Potter maelstrom is one of cultural as well as literary exchange. This has given rise to gems like the rendering of ‘Tom Marvolo Riddle’ as ‘Tom Elvis Jedusor’ (French) and ‘Romeo G. Detlev Jr’ (Danish); of the Hogwarts houses as ‘Lleurerol’, ‘Slafenog’, ‘Crafangfran’ and ‘Wfftipwff’ (thanks, Wales); and not forgetting Harry Potter agus an Órchlach (because why have two words when you can have one plus a fada).

It has also given rise to a passionate, global fandom which is just as vibrant now as it was a decade ago at what should have been the height of Potter fever – the publication of the final book, Harry Potter and the Deathly Hallows. It may have started with book clubs or midnight releases, but being handed page upon page of a captivating fantasy world just singing with tantalising possibility soon inspired an appetite and enthusiasm to match. The ranks of the Harry Potter fandom swelled online, which seemed like the only place big enough to contain such communal outpourings of fan art and fiction. In its heyday, it spilled over into fansites, music (including full-length musicals and a whole genre known as wizard rock), parodies, conventions and even Muggle Quidditch leagues. These days, its audience may be a little less fervent – the lack of long, delirious waits for the next book release or the rabid urgency of needing to compose plot-heavy fan theories usually allows a greater sense of calm into fandom – but it remains passionate. Newer media like podcasts and fan-funded films have chimed in, but it is almost impossible to overstate the importance of classic fan media to the Harry Potter community. Art in particular continues to blossom with new interpretations of characters by veteran and developing artists alike.

Of course, the Wizarding world has had more ‘official’ afterlives, too. Rowling, while moving on to other writing projects, seems to have long given up trying to shake off the shadow of the series that made her famous: it’s simply too large and culturally significant to forget. First came the films, then theme parks, studio tours, Pottermore.  The spin-off nobody asked for (but everyone went to see), Fantastic Beasts and Where to Find Them (2016), itself based on a short spin-off book. And of course, Harry Potter and the Cursed Child, a spectacular but divisive project. Nominated for a record 11 Olivier awards but leaving some readers of the separately published playscript disappointed, it’s a tricky, somewhat exclusionary medium with which fans have been left to deal. It has, however, made Harry Potter perhaps one of the only children’s series in history to so thoroughly dominate shelves, screens and stage. It’s made the Harry Potter fandom one of just a handful who have received  much more – more opportunities, more material – than the original seven-book series promised.

But such an official afterlife could not have survived without the energy and sheer size of the Harry Potter fandom itself. The Harry Potter franchise is not the gift that keeps on giving, it’s the one that keeps on taking: your money, your time, your hopes and dreams (where is my edgy-yet-adorable Tonks and Moody buddy Auror television miniseries, Rowling? where is it?). It’s fandom that keeps giving, as fans old and new discover ways to invent, re-envisage, explore and critique the sensation. When British actress Noma Dumezweni was cast in her now Olivier-winning role as Hermione in Harry Potter and The Cursed Child, it was something this fandom had seen before, because black Hermione – complete with ‘light reading’ and Afro – is an interpretation that has been cropping up in fan art for years. In fact, it’s doubtful that a majority-white canonical cast – too popular for most criticism or alteration to make a mainstream difference – would have been re-envisioned if fans had not already expressed consistently and visually their belief in a re-imagining of their beloved Hermione.

It is part of fandom’s power to lend thousands, if not millions, of different imaginations to what was once just one. In choosing to capitalise on the persistence of Potter fandom, Rowling has merely underlined its desire to express and re-imagine Harry’s world, including in ways she never expected. It is a phenomenon which lives on, and will continue to live on. If its twentieth anniversary means anything – and plenty of twentieth anniversaries of famous books pass by completely unnoticed – it is this: discovering the boy with the lightning scar is an experience, not a moment. It is only because of fans’ enduring enthusiasm that any fictional world can spring to life, let alone feel as important and relevant years after it first appeared as this one does.