In order to acquaint himself with his three lead actors, director Alfonso Cuarón had each of them write an essay about their characters, from a first-person point of view. Emma Watson, in true Hermione fashion, went a little overboard and wrote a 16-page essay. Daniel Radcliffe wrote a simple one-page summary, and Rupert Grint never even turned his in.
Alfonso Cuarón had the idea that when the dementors approached the Hogwarts Express the rain would turn to ice, however, due to his thick Spanish accent the visual effects team misheard "ice" as "eyes". They went as far as to draft a storyboard which depicted eyes falling from the sky, which they presented to a stunned Cuarón, who instantly corrected their mistake.
Azkaban Prison, though mentioned, never actually appears in the film. Nonetheless, concept art was created by both conceptual artist Andrew Williamson and production designer Stuart Craig. Both sketches depict Azkaban as a triangular stone fortress built on the edge of a giant waterfall. When Azkaban is seen for the first time in Harry Potter and the Order of the Phoenix (2007) the filmmakers looked to these sketches and ultimately decided to keep the triangular design but relocated the prison to an island in the middle of the ocean (closer to how it was described in the book).
During the filming of the sleeping bag scene, director Alfonso Cuarón and Alan Rickman played a practical joke on Daniel Radcliffe by hiding a remote-control-operated Whoopee Cushion in his sleeping bag. According to Cuarón, Daniel tried really hard to stay in character while everyone else was laughing.
Alfonso Cuarón had an idea for there to be tiny people inhabiting Hogwarts, and jumping on piano keys in one scene. J.K. Rowling firmly vetoed it, saying tiny people were completely foreign to the world of her books.
It was Alfonso Cuarón's idea to have a Hogwarts Choir singing as the students enter the school, and he suggested using "Double, Double Toil and Trouble" from William Shakespeare's Macbeth. John Williams agreed, so the tune - and lyrics - ended up being used throughout the film, titled "Double Trouble". The Shakespeare/Macbeth motif went so far that that the film was marketed under the tagline "Something wicked this way comes".
During the scene where we first meet Buckbeak the Hippogriff, just after Ron pushes Harry forward there is a shot of the animal pooping. The CGI team believes this might be the first example of a CGI animal doing this, but the BBC miniseries Walking with Dinosaurs (1999) had done it first.
The effects team spent six months creating the dementors. Originally, Alfonso Cuarón wasn't thrilled with the idea of using CGI and wanted to use more traditional techniques such as puppetry. The filmmakers tried a basic technique with a dementor puppet floating in the breeze but weren't satisfied with the way it looked. Puppeteer Basil Twist showed them a technique that involved putting the puppet in water and shooting it in slow motion with the film reversed. The filmmakers liked the way it looked but realized that this would be an impossible task, so in the end they decided to use CGI to create the dementors.
Much of the filming was done in Scotland, so the filmmakers wanted to be sure that a Highland Cow, a breed of cattle native to Scotland, appeared in the film. The large, hairy animal with big horns can be seen in front of a shop in Hogsmeade when Ron and Hermione go and look for Harry after he leaves the pub.
Honeydukes "is floor-to-ceiling psychedelia" and includes Mexican skulls made of sugar. The cast was told that the Honeydukes candy was lacquer-coated, when in fact it wasn't, to prevent candy from disappearing between takes.
Professor Dumbledore seemingly stalls the executioner by saying that he needs to sign the execution order, and that he has "a very long name". In Harry Potter and the Order of the Phoenix (2007), his full name is revealed to be Albus Percival Wulfric Brian Dumbledore.
The script for this film makes no mention of Professor Flitwick. Wanting to keep Warwick Davis involved, director Alfonso Cuarón came up with the idea of having him play the choir director. In the next film, Mike Newell liked the look of the choir director and wanted to keep using it. Therefore, the choir director became Flitwick, and his new look has been used for all the subsequent films.
The rating in the Netherlands for this film is "not under 9". This rating was created especially for the film, since it was judged to be too scary for 6 year olds and the next rating, "not under 12", would exclude too much of the target audience.
Shot entirely on wide-angle lenses. The length of the lenses ranged between 14-24mm and never beyond that. Alfonso Cuarón insisted on the wide-angles because he wanted to let the audience see the foreground and the background.
Although the stone circle seen in the Hogwarts Grounds was a creation of the filmmakers, it was based upon actual stone circles found throughout Britain (i.e. Stonehenge). The stones were created at Leavesden and were delivered by helicopter to Glencoe, Scotland, where they were set into holes dug into the ground. They looked so realistic that the young actors ultimately asked director Alfonso Cuarón if the stones were the reason why he picked that particular location. "It's always gratifying when your work is mistaken for the real thing!" said art director Alan Gilmore.
The lyrics to the song playing in the opening feast at Hogwarts come from William Shakespeare's famous play Macbeth. The lines in the play are spoken by witches, who are called the "Weird Sisters". In the novels, the Weird Sisters are a popular wizarding band.
Illusionist Paul Kieve served as a consultant. He taught magic to several members of the cast including Daniel Radcliffe and Emma Watson (Harry and Hermione) and worked extensively to create physical magical effects. He is the first illusionist to have worked on any of the series of films. He also made a cameo appearance in the film in the scene in the Three Broomsticks pub.
In the scene where Harry is given the Marauder's Map by the Weasley twins, the name "Moony" is misspelled as "Mooney". While not really a mistake, there is still an interesting connection. The film's visual effects supervisor is named Karl Mooney. The spelling was changed deliberately for the in-joke.
Ron's dream about spiders making him tap-dance is a two-in-one reference of the next book. In 'Goblet of Fire' there is an unforgivable curse where you can control what someone does, taught by Professor Moody. He makes a spider tap-dance on the desk.
After the death of Richard Harris, many actors were considered for the vacant role of Albus Dumbledore. Christopher Lee was in the frame for a while, and there was a rumor (reported in many newspapers) that Ian McKellen was also considered. The Harris family wanted Richard's longtime friend and peer Peter O'Toole for the role but there were studio concerns over insuring O'Toole for the remaining five films. Richard Attenborough also lobbied for the role but was ultimately turned down.
When we see the Marauder's Map for the first time, the name 'Newt Scamander' can be seen. In the Harry Potter universe, he wrote the book "Fantastic Beasts and Where To Find Them", but isn't a teacher at Hogwarts.
This film actually marks the second time that Michael Gambon has replaced Richard Harris. Harris had previously played Inspector Jules Maigret in Maigret (1988), while Gambon took over the role in the television series Maigret (1992).
Sir Cadogan, played by Paul Whitehouse, was cut almost completely out of the film. You do still see Sir Cadogan jump into the shot of Ron, Harry and Hermione right after Ginny tells them the Fat Lady is gone. He appears in a picture behind them.
Among the difficulties associated with filming in Scotland was the amount of rain that fell during the shoot. During the breaks in filming, helicopters delivered large bags of gravel to the set in order to prevent it from washing out. Many of the filmmakers were concerned as to how this would affect the look of the film, although director Alfonso Cuarón and cinematographer Michael Seresin insisted that it was the best look that they could have come up with.
Production designer Stuart Craig has revealed that the appearance and location of Hagrid's Hut as seen in this film and subsequent films was closer to his original design for the hut, which had been compromised for the first two films due to the scenes being filmed in a small patch of land outside the studio, rather than on location in Scotland.
Two Knight Buses were built: one for exterior shots and one for interior shots. The exterior of the bus was created by taking an ordinary double-decker London bus, adding a level, and painting it purple.
The Dursleys have three television sets in their house; one in the living room, one near the dining table, and one in the sunroom. While not mentioned in the film, it is explained in the book that Dudley complains about the long walk from the fridge to the television in the living room.
The design of the large clock which functions as a visual motif in this film appears to be based on the Old Town Clock (also called the "Orloj" - pronounced "OR-LOY") in Prague, Czech Republic. The Orloj tells not only the time, but shows the month, the sign of the Zodiac, and shows the relative positions of the moon and sun.
Subplot involving the Sneakoscope concept from the novel, as well as an attempted attack on Ron in his sleep at Hogwarts by Sirius Black, were filmed (and can be partially found as additional scenes on some DVD versions) but ultimately scrapped from the finished version. Oddly enough, a small bit from the latter, Harry's lines about missing a chance to capture Black, was still featured prominently in most promotional trailers. (Source: 2-Disc DVD extras & trailers).
Although most of the Hogwarts scenes were filmed on studio sets (unlike the previous films which were shot largely on location), the geometric staircase at St. Paul's Cathedral, London, was used as the staircase that leads to the Divination classroom.
The German subsidary of Warner Bros. tried to cut down the film (as they did with Harry Potter and the Chamber of Secrets (2002)) to secure a more commercial "Not under 6" rating. They submitted several versions but all were rejected by the German ratings board FSK for this rating. In the end the uncut version was released with a "Not under 12" rating.
the singer (formerly of The Stone Roses) appears briefly in the bar at the start of the movie reading "A Brief History of Time" by Stephen Hawking. He was originally cast as the pub landlord, but the role was cut right down due to timing issues.
References to director Cuarón's Mexican nationality abound. On the fountain in the courtyard in front of the clock tower, there are several statues of eagles eating snakes, as on the National Seal of Mexico. Also, among the many candies offered at Honeydukes are skulls made of sugar, which are a popular treat in Mexico on "El Dia de los Muertos," or the Day of the Dead. And, after Dumbledore says his final lines outside the infirmary, he goes down the stairs humming "La Raspa", the Mexican Hat Dance.
The trivia items below may give away important plot points.
Although the Marauders' Map, created by Messrs Moony, Padfoot, Prongs, and Wormtail plays a large part in the film, the identities of the first three are not made clear. This is surprising as this was important to understanding this plot in the book. Moony was Lupin, who was supported by his three friends. These learned "Animagus" shape shifting techniques to sympathize with him. James Potter was Prongs the Stag (a trait passed on to the Patronus of his son Harry), Sirius Black was Padfoot the Dog, and Peter Pettigrew was, more obviously, Wormtail the Rat.
Early in the film, Harry sees a newspaper article with a photograph of the Weasley family in Egypt. Though it is never again mentioned, this is a very important plot point in the book. While on an inspection of Azkaban the Minister of Magic had a copy of that paper, and gave it to Sirius Black who recognized Peter Pettigrew disguised as Scabbers. This is what made him decide to break out of Azkaban, track down Scabbers at Hogwarts, and take his revenge by killing him.
Lupin says that he was very close with Harry's mother. This may seem at odds with the book's story that Lily Evans was a close friend of Lupin's rival Severus Snape. However, J.K. Rowling revealed that after graduating from Hogwarts, Lupin still found it difficult to find paying work, because nobody wanted to employ a werewolf. James and Lily, therefore, financially supported him.
The ending of the film, in which Sirius escapes on Hagrid's hippogriff, is actually a reversal of the opening of Harry Potter and the Sorcerer's Stone (2001), in which Hagrid arrives on a flying motorcycle which, the book reveals, he borrowed from Sirius.
Despite featuring the idea of a mass murder as the back story, this is *arguably* the only book/movie in the series where no person dies in the story itself. The argument is that, while the villain in Harry Potter and the Chamber of Secrets (2002) was destroyed, he was a ghostly automaton who was, perhaps, never alive to begin with.