EVER found yourself thinking what would have happened in Outlander if the Jacobites had won at Culloden?

Or maybe, when you were reading the Harry Potter books, you pondered about how the story would have unfolded if only Cedric Diggory had touched the Triwizard Cup?

Or perhaps during the last series of Games of Thrones, you just simply wished it wasn’t so patchy.

Well, alternatives to the stories you know are available.

Tomorrow marks the seventh annual International Fanworks Day, celebrating the creators and consumers of fanfiction.

It was established by the Organization for Transformative Works, the non-profit behind the vast, sprawling Archive of Our Own (AO3), home to more than seven million stories set in pre-existing worlds.

A fair chunk of those take place in well known franchises – Marvel, Doctor Who, Disney – adding to the story or doing new things with familiar characters.

One writer has a 25,000-word tale which relocates Obi Wan Kenobi to Saltcoats in 1855.

Dr Matthew Sangster from Glasgow University’s Centre for Fantasy and the Fantastic, said the two main impulses behind fanfiction were “more or different”.

He added: “A lot of fanfiction fills out aspects of the world that the author leaves sketched in, so it tells the story of all the more boring days at Hogwarts where Voldemort is not intervening.

“Or they’ll think ‘the author went this way, I think it would have been more interesting if they’d gone this way’.”

Sangster says that means sometimes expanding on relationships hinted, or to make spaces in franchises for the kinds of identities not there originally, allowing, for example, queer creators to write in the kinds of character interactions missing from mainstream media.

Maybe there’s a trans science officer on the USS Enterprise, or a gay Avenger.

A lot of fanfiction is also sexually explicit.

Maybe that’s one thing when it’s Captain Kirk getting it on with Spock, but it’s a little more controversial when it involves real people.

There’s a huge stooshie in socially conservative South Korea just now, over writers sharing Real Person Fiction (RPF) same-sex fantasies about K-Pop bands.

And the breadth of celebrity being written about is surprising. On AO3 there’s even someone’s (fictional) yarn about an erotic encounter with Ian Blackford at a BP Garage.

Claudia Rebaza from the Organisation for Transformative Works told the Sunday National the need to tell stories was “as old as mankind itself”.

She said often stories were “drawn from familiar tales that people already knew”.

She added: “This sharing of familiar stories created a community among strangers or strengthened bonds among friends and families.

“Similarly, an important part of fanworks is in the sharing and enjoyment.”

Some writers have broken through from fanfiction to mainstream success. Most famously EL James ditched the vampires and werewolves from her Twilight story Master of the Universe and turned it into the globally massive Fifty Shades of Grey.

Yet, despite the huge numbers writing and reading, and despite its influence on Hollywood, there’s still a snobbishness towards the works.

“There’s some very strong academic arguments about why it’s useful and why it’s not actually very different from many other species of composition,” Sangster argues.

“We’re still stuck on the romantic originality model where authors are supposed to channel their ideas from nowhere, but no one actually does that, everyone’s building on existing cultural literacies and fanfiction is just more explicit about that.”