Even after all these years, the tale of the boy wizard Harry Potter continues to confound us all.

It's been more than 20 years since the first Harry Potter book was published, but the passion and enthusiasm that Potter fans had for the series all those years ago shows no signs of dimming.

So voracious is our appetite for more stories of the wizarding world, there's even been a spinoff series of movies - Fantastic Beasts and Where to Find Them - and several companion short stories penned by JK Rowling.

Meet the woman who remembers the Harry Potter series word-for-word:

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Fans can ride theme park attractions dedicated to Potter and visit sets where the movies were filmed, yet still we return to those original seven magical books time and time again.

You might think that every Easter egg and wrinkle in the eight Potter movies would have been discovered by now, but if one eagle-eyed fan's recent Reddit post is anything to by, there are still more secrets for us to uncover.

This particular revelation centers around the Marauder's Map - a magical piece of parchment created by Harry Potter's father and godfather, along with Remus Lupin and Peter Pettigrew. It shows a map of Hogwarts in real time, as its occupants move about the castle.

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The makers refer to themselves as Moony, Wormtail, Padfoot and Prongs, though if you look closely at one blink-and-you'll-miss-it moment from the Prisoner of Azkaban movie, you'll notice that 'Moony' is spelled incorrectly on the map.

Moony is spelled thus in the books and generally in print, though on the map in the movie is spelled 'Mooney'. The Redditor in question expounds on this in a post on the r/MovieDetails subreddit, claiming that the 'mistake' is actually an intentional nod to the visual effects supervisor of the film, Karl Mooney.

They wrote;

"Harry Potter and the Prisoner of Azkaban(2004): when Harry is shown the Marauder's Map by the Twins for the first time, it spells MOONY incorrectly and instead says MOONEY which is a nod to the visual effects supervisor of the film: Karl Mooney"

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"That’s a very neat piece of info." Wrote on Redditor.

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This isn't the only moment from the Prisoner of Azkaban movie that has given fans pause for thought of late. One fan took to Twitter to reveal that they had just discovered an altogether rather raunchy moment in the movie.

"Day ??? of the lockdown. I found the secret sex scene in Harry Potter and The Prisoner of Azkaban [sic]," they wrote.

"In the bottom left hand corner of the Marauder's Map at 2hr and 20 min mark there are 2 sets of footprints who seem to be making out or possibly having sex," the Twitter user continued.

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So yes, we're still discovering the secrets of the Harry Potter series, even after all these years.

Harry Potter fan spots 'mistake' in 'Prisoner of Azkaban' film, says producers sneaked it in