Harry Potter fans have been alerted to a blink-and-you'll-miss-it mistake in one scene from the popular film franchise - but it turns out it may in fact be an Easter egg hidden in the movie by the producers.

In the adaptation of J.K. Rowling's third book Harry Potter and the Prisoner of Azkaban, Harry is seen trying to sneak out of the school to get to Hogsmeade using an invisibility cloak.

His footprints in the snow are spotted by the Weasley twins, Fred and George, who drag Harry back inside explaining they have a better way of helping him go unnoticed.

The brothers introduce him to the Marauder's Map, a magical parchment showing Hogwarts, seven secret passages into the castle and the movement of people inside the school.

They give Harry the secret phrase to reveal the map's details
It is branded with the nicknames of the four former students who created it

It was created by Remus Lupin, Peter Pettigrew, Sirius Black and James Potter during their time as students, with their nicknames inscribed on the front.

Eagle-eyed viewers may have noticed that Remus' nickname Moony appears to have a spelling error when it appears on the front of the parchment in the 2004 film.

But one fan has claimed the 'E' placed in the name in the screen version is actually an intentional nod to the visual effects supervisor of the film, Karl Mooney.

Remus is given the nickname by his fellow Marauders due to his transformations during every full moon, and it is always referred to in text as 'Moony'.

So it appears the special effects team couldn't resist the temptation to hide their own little tribute in the screen version.

It's not the first time fans of the series have questioned an error, after 500 hardback copies of Harry Potter and the Philosopher's Stone were printed with an error on page 53.

In Harry's list of school supplies, the repetition of "1 wand" made it a sough-after collectors piece, with one copy of the book being expected to fetch up to £20,000 when it went on sale.