Viewers Notice Hilarious Mistake In Harry Potter Reunion

But some eagle-eyed viewers became were left scratching their heads during a segment involving James and Oliver Phelps, who played the Weasley twins, Fred and George.

Where it should have said the actors' real names, the producers of the doc seemed to have got the pair mixed up, ya know, because they're twins and that. Oh how embarrassing.

Sharing a clip from the documentary, one person wrote on TikTok: "@hbomax pls tell me it’s made on purpose."

Luckily, it seems that it wasn't actually the cock-up it appeared to be at first.

Oliver Phelps posted a snap of the mix-up to his Instagram account over the weekend, hinting at what could have been going on.

He said: "I guess after all those pranks over the years somebody decided to get their revenge."

Commenting on the post, co-star Matthew Lewis, who played Neville Longbottom, said: "This is legit hilarious."

But who was the responsible for the prank?

Well, it appears as though it was none other than Draco Malfoy himself.

Admitting his part in it all, actor Tom Felton said: "It was my doing."

It's not the only strange moment fans spotted while watching the film, though.

Watson, who played Hermione Granger in the films, was discussing her childhood when an image of a young girl wearing some Minnie Mouse ears appeared on screen. While very adorable, the photo is very much not Watson and is actually an image Roberts posted of herself on Instagram a while back.  

And it didn’t take long for fans to notice, posting on Twitter, one person wrote: "Not the editing crew on Harry Potter 20th Anniversary putting a photo of f**king Emma Roberts as a child not Emma Watson. I’m screaming."

Someone else asked: "But my goodness, couldn't the producers/writers/whoever fact check? They showed a picture of young Emma Roberts thinking it's Emma Watson."

A third wrote: "They put the famous Emma Roberts picture in the reunion that almost everyone thinks it’s Emma Watson, What the actual f**k? I can’t believe this."

Elsewhere, Watson admitted that she actually had a huge crush on Felton during filming.

"I walked into the room where we were having tutoring and I just don't know how to say it - I just fell in love with him.

"I used to come in every day and look for his number on the call sheet, it was number seven, and if his name was on the call sheet it was an extra exciting day."