Stuart Little fans lose it as they discover major change depicted in the movie

Fans of Stuart Little have been left reeling after discovering a big change between the book and the film.

The film sees the titular Stuart Little being adopted by the Little family, before going on all sorts of adventures, as well as misadventures involving the family cat.

The cat is, of course, determined to catch Stuart because he is a mouse, albeit a very polite and sweet-natured talking mouse.

You might think that there is one thing that everyone knows about Stuart Little - he's a talking mouse who the Little family adopts.

Except people are finding out something about the original book that the film was adapted from that has left them absolutely reeling.

It seems that everything you thought you knew about Stuart Little in the films is very different from the books.

Stuart Little was adopted by the Little family in the films, but fans have realised not all is as it seems (Columbia Pictures/Getty Images)

That's because in the book published by E.B. White in 1945, Stuart Little is not actually a mouse - he's a boy who happens to be very small and look like a mouse.

And that's not even the half of it, either - alarmingly.

Because in the book, Stuart is not adopted by the Little family. Oh no, his mom just gives birth to a baby who is two inches tall and looks like a mouse.

You'd really think that would come up on the ultrasound, but then I suppose they didn't have the ultrasounds we have today in 1945.

The passage from the books says: “When Mrs. Frederick C. Little's second son arrived, everybody noticed that he was not much bigger than a mouse.”

It continued: “The truth of the matter was, the baby looked very much like a mouse in every way.

"He was only about two inches high; and he had a mouse's sharp nose, a mouse's tail, a mouse's whiskers, and the pleasant, shy manner of a mouse.”

Well, that's considerably weirder than the Littles adopting him and his parents also being talking mice.

The cover of the Stuart Little book (Scholastic)

Fans have reacted with a mixture of horror and hilarity that the one thing they thought they knew about Stuart Little turned out to be wrong, at least in the book, and took to social media to share their thought.

One played into what must have been quite a shock, joking: "Finding out Stuart Little is actually a tiny human that just looks like a mouse feels less ‘children’s book’ and more the family made a deal with something and agreed to raise whatever showed up.”

Others just straight up refused to accept the truth, with one saying: “That's just not right. Not right at all. No, sirree, Bob."

Meanwhile another said: “All those mouse shenanigans were human shenanigans??”

It also paints the cat trying to eat Stewart in a very different, and horrifying, light.