Amazing 'Prisoner of Azkaban' facts as the best Harry Potter film turns 15

This week marks fifteen years since the release of Alfonso Cuarón’s adaptation of JK Rowling’s Harry Potter and the Prisoner of Azkaban. It was well received on release, and time has not diminished its reputation.

Actually, if anything, it’s increased over the years, with many critics and fans considering it to be the best of the series. It certainly has some of the most interesting behind the scenes stories, as the following facts reveal.

Cuarón thought the project was a joke, which made Guillermo del Toro tell him off

During the promotion period for Netflix’s Roma, Alfonso Cuarón revealed an early conversation he had with Guillermo del Toro about Azkaban.

“I said, ‘I’m going for Harry Potter, can you believe it? And I even made fun of it. I hadn’t read the books or seen the films. And then he looks upset with me. He called me flaco, that means skinny [in English].”

“He says, ‘F***in’ skinny, you’re such a f***in’ arrogant bastard. You are going right now to the f***in’ bookshop and get the books and you’re going to read them and you call me right away,'” Cuarón said. “When he talks to you like that, well, you have to go to the bookshop.”

Cuarón read the books, and halfway through Azkaban, he realised the opportunity that was in front of him.

“As a filmmaker, it was almost like a lesson of humility, of saying how am I going to do it my own, but at the same time, respecting what has been beloved in those couple of movies.”

Emma Watson punched Tom Felton for real

It’s one of the most satisfying moments in the movie. So satisfying, in fact, that it got a big cheer at the film’s premiere. But the moment where Hermione punches Malfoy was an unscripted moment.

"She’s got a mean right hook, that girl," Felton said. "It was originally a slap I think, so I said, 'Let’s test it out now. Give me a slap and try to work on it,' meaning give me a screen slap, a fake slap. But she actually smacked me on the face pretty hard, and I walked away with my hearing impaired, and my tail tucked between my legs."

Alfonso Cuarón made the cast do homework

During the pre-production period, Cuarón insisted the three main stars write essays about their characters as part of their preparation. Appropriately, Emma Watson wrote a 16-page thesis. Daniel Radcliffe did the bare minimum, writing a single page. Rupert Grint, meanwhile, didn’t bother to write one word.

Still, according to Grint, “it’s quite Ron-ish not to do it. I think [Cuarón] kind of appreciated that.”

Cuarón had to enforce himself not to swear on set

Previously, Cuarón had only worked with adults in his film career - developing a reputation for being a potty mouth. So much so, that there was a rumoured clause in his contract that stated he wouldn’t be allowed to swear on set, but it sounds like it was more of a self-imposed ban.

“I had to restrain my language a little bit, because I have a very foul mouth,” Cuarón said. “I had to restrain my language in English, but I would say things in Spanish. Actually, they learned quite a lot of curses in Spanish. But that was the only thing and even if I cursed… They've heard it before. That was the only point of disadvantage in our relationship, that they would curse and I couldn't!”

Robert Pattinson probably should have been in the film

Robert Pattinson’s Cedric Diggory appears in the book, but doesn’t appear in the film - or does he? Well, Robert Pattinson certainly doesn’t, but the character technically does.

We do see a Quidditch game, which does feature a Seeker on the Hufflepuff Quidditch Team, which should have been Diggory. The actor who plays the unnamed character is uncredited.

We know Cuarón hadn’t read any of the books before being asked to make the film, so maybe he didn’t get further than Azkaban when he did his GDT inspired research, and didn’t realise how significant Diggory would go on to be.

The film contains accidental foreshadowing

While talking about her reaction to the film, JK Rowling praised Cuarón, and revealed a surprising element of Azkaban’s script.

"Alfonso [Cuarón] had very good intuition about what would and wouldn't work,” Rowling said. “He's put things in the film that, without knowing it, foreshadow things that are going to happen in the final two books. So, I really got goosebumps when I saw a couple of those things and I thought people are going to look back on the film and think those were put in deliberately as clues."

It’s never been officially confirmed what those moments were, but now we know what happens in the last two books, it’s pretty easy to guess.

The conversation between Harry and Lupin on the bridge (that’s not in the original book) is definitely one of them.

Not only does it give insight into Harry’s parents that would become relevant after the Snape reveal, it ends with Lupin saying, "You're more like them than you know, Harry. In time you'll come to see just how much.”

That clearly foreshadows Harry’s Deathly Hallows sacrifice.

Christopher Lee and Ian McKellen both turned down Dumbledore

Following Richard Harris’ tragic passing, a replacement Dumbledore was needed for Azkaban. And some iconic names were approached.

Christopher Lee turned the part down because of scheduling conflicts, and wasn’t happy when the news hit the press. "I consider this matter in very bad taste. The man had only been dead for about 10 days when this gossip started to go round," he said.

Ian McKellen has his own reasons for turning the part down. “When they called me up and said would I be interested in being in the Harry Potter films, they wouldn't say what part but I worked out what they were thinking. I couldn't take over the part from an actor who I know disapproved of me.”

Harris had previously described McKellen as ‘technically brilliant, but passionless.’

Alfonso Cuarón and Gary Oldman designed Sirius’ look

Gary Oldman’s big screen take on Sirius Black is pretty different to the description of the character in the book.

There, he has "a mass of filthy, matted hair hung to his elbows. If eyes hadn't been shining out of the deep, dark sockets, he might have been a corpse. The waxy skin was stretched so tightly over the bones of his face, it looked like a skull. His yellow teeth were bared in a grin."

Yeah, that doesn’t really sound like the rock-star we got in the movie. As it turns out, Cuarón and Oldman collaborated on the character’s style, with Cuarón designing Black’s tattoos, with Oldman responsible for the hair.

Together, they created a truly memorable look for the character.

M. Night Shyamalan almost made the movie

Warner Brothers’ pursuit of Shyamalan for Azkaban might seem pretty bizarre, but it sort of made sense at the time. Azkaban was intended as a darker, more grown-up movie, to reflect the dark themes of the book, and Shyamalan was coming off the back of the successful Sixth Sense and Signs.

Though, considering The Last Airbender, The Happening and Lady in the Water were all in the director’s near-future, this was probably a lucky escape.

Alfonso Cuarón told Daniel Radcliffe to imagine Cameron Diaz in a g-string

Bit of a weird one this, but in order to get a key shocked expression on Daniel Radcliffe’s face, Cuarón asked the young actor to picture his current crush, Cameron Diaz, in a revealing swimsuit.

“That got out!” Cuarón said when confronted with the on-set tale. “I don't believe in being very precious when you are dealing with kids… Kids hate to be patronised. They just want to be treated like anybody else. They know if I have an argument with someone it’s just adults having a stupid argument, you know? That is the relationship I had with them, it was just to be very straight.”