10+ 'Harry Potter And The Prisoner Of Azkaban' Behind-The-Scenes Secrets That Only True Fans Knew

Those of you who have read the books will probably know that Sirius Black doesn't look much like his novel counterpart.

It was director Alfonso Cuarón who designed his tattoos and it was, in fact, Gary Oldman that designed the hair.

Gary Oldman only did the role to impress his kids.

Said Oldman in an interview: "You become incredibly cool to your kids, and you get a young fan base. So you became the cool dad at school."

It actually had to do with the fact that Dumbledore's original actor, Richard Harris, hated his acting.

It's all very Bette Davis and Joan Crawford, however a lot more British.

Sir McKellen said:

“Seeing as one of the last things [Harris] did publicly was say what a dreadful actor he thought I was, it would not have been appropriate for me to take over his part. It would have been unfair.”

Or at least, that's what J.K. Rowling based them on.

In fact, the way that the dementors attack their prey is how she felt while she was depressed: like something was sucking out her soul.

Of course, we got a much better version of that scene.

And it was a mutual agreement between Emma Watson (Hermione) and Tom Felton (Malfoy) that it should be turned into a punch.

This was, of course, out of respect for the actor's young age.

He was used to working around adults, so it was a little hard for him. He even had to throw a swear jar on set.

Believe it or not, it was actually Michael Gambon and Alan Rickman who did it!

They set up a fart machine behind Radcliffe when he was supposed to have a close-up done, and let it rip when he was doing his scene.

The filmmakers made the mistake of making the Hogwarts Express available to the public and boy did they pay for it.

Smashed windows and spray paint delayed production for some time.

We all remember Robert Pattinson as Cedric Diggory in The Goblet Of Fire, however, in The Prisoner Of Azkaban, he's nowhere to be found even though his character is. Instead, they got some random actor.

You might hate doing them (I don't) but it sometimes helps actors understand their characters more.

That's what Emma Watson, Daniel Radcliffe, and Rupert Grint were asked to do about their characters by Alfonso Cuarón.

Each approached the essay as their character would.

Watson went above and beyond with her task, while Radcliffe completed the bare-minimum. On the other hand, Rupert Grint did not even hand in the assignment!

For once, Dudley Dursley keeps his mouth shut.

As in, he has absolutely no lines in this movie. Sure, he's seen in the background watching TV but besides that, he's practically inconsequential.

You'd think directing such a huge franchise, you'd have to read at least one book.

This was not the case for Mr. Cuarón. In an interview with IGN, he said: "I just thought that it was a big, big kid's franchise. I thought it was something really silly".

During the time the movie came out, M. Night had a burgeoning career.

The studio was really targeting him to direct, however, he turned it down to focus on his own movies.