Whereas Harry Potter and the Chamber of Secrets followed the first Harry Potter film’s template to a T and turned around a quick yet robust sequel, the adaptation of Harry Potter and the Prisoner of Azkaban is where the series began to branch out stylistically, play to the strengths of its developing stars, and take advantage of a longer 18 month production cycle which would become the standard spacing between releases. This third installment in the Harry Potter series features a new director, Alfonso Cuarón (also director of the 1995 WB adaptation A Little Princess as well as 2013's Gravity), who took advantage of the story's outdoor scenes filmed in the breathtaking Scottish Highlands and helped paint a lighter, subdued color pallet which was carried forward in future films and coalesced brilliantly under the moonlight in contrast to the darkness and shadow which creeps into the story in this pivotal tale.
Cuarón's contributions to the cinematic series went far beyond the visuals, however, as he spent a lot of time with the three lead actors and encouraged them to bring individuality to their roles and wear their own casual [Muggle] clothing on sets outside the Hogwarts classrooms. There's a great story that when Alfonso Cuarón came on as director he gave the actors an assignment to write an essay about his or her character. Daniel Radcliffe came up with 1 page, Emma Watson wrote an impressive 16 pages, and Rupert Grint never even wrote the bloody paper, explaining that Ron Weasley wouldn't have done his homework. This amusing anecdote speaks to the fact that by this point in time these actors had really taken on the personas of Harry, Ron, and Hermione, and at age 14-15 The Prisoner of Azkaban is the film where their relationships really begin to come alive on screen.
The third novel introduced a number of significant characters to the thickening plot, and Gary Oldman, Timothy Spall, David Thewlis, and Emma Thompson joined the cast as the recurring characters of Remus Lupin, Sirius Black, Peter Pettigrew, and Sybill Trelawney, alongside Michael Gambon who tackled his first film as Albus Dumbledore with poise. Gary Oldman is downright unrecognizable as Sirius Black; it's amazing how well this actor can sink into a role and take on the shape and persona of a character. In contrast, Timothy Spall has the natural appearance of Peter Pettigrew, and his rat-like mannerisms and pathetic pleads are performed with alacrity. Thewlis and Thompson live up to the memorable personalities of the professors from the novel and lead sterlingly in the Defense Against the Dark Arts and Divination classroom scenes. In particular, Thewlis and Radcliffe have great chemistry, and Harry shouting Expecto Patronum! as he conquers the patronus charm while practicing with Professor Lupin is among the most memorable moments in the entire film series. Scenes like this one which enhance the emotional impact of the events from the novels give the Harry Potter movies an occasional edge over the books.
John Williams returned to compose his third and final Harry Potter score, but his work on The Prisoner of Azkaban marks somewhat of a departure from the first two films. There's a lot more variety in the music here, and the classic Williams sound is less recognizable as many numbers back off from the full orchestra and opt for simpler or more daring arrangements. For example, there's an interesting medieval style on "Hagrid the Professor" and prominent use of flute on "A Window to the Past". The jazzy, chaotic "Knight Bus" which features an accordion section is one of the most memorable tracks on the score; in fact, nothing else in the other movies jumps out quite like it. There are still plenty of traditional, vivacious Williams numbers on exciting moments such as "Buckbeak's Flight", "The Whomping Willow and the Snowball", and "Quidditch, Third Year", but these numbers are spread out giving the viewer a chance to relax and enjoy the quieter moments and occasionally slower pace set forth by director Alfonso Cuarón. Overall, The Prisoner of Azkaban has a more dynamic score that opens up the film to have more breathing room outside the Hogwarts castle and also helps transition from the traditional John Williams compositions to those of the musicians who would take his place in the final five films of the series.
At the start of term feast, the Hogwarts choir sings “Double Trouble” which provides school atmosphere but feels a bit cliché that actual witches and wizards would sing of "double, double, toil, and trouble" and "something wicked this way comes". Interestingly enough, these lyrics were taken from a spiritual incantation from Shakespeare's Macbeth. While the presentation of Hogwarts extra curricular activities is appreciated (the toads are a nice touch), this song is a bit annoying to hear for a second time in the closing credits. Speaking of, the ending credits scene with names appearing on the Marauder’s Map is beautifully animated and easily the best-looking credit sequence of all the movies. This closing meditation on what's debatably the most useful magical device Harry acquires at Hogwarts is well-advised. The next film tried to copy this credit sequence with names coming out of pieces of paper from the goblet of fire, but the Marauder's Map credits are much more intricately designed and entertaining to watch.
In Harry Potter and the Prisoner of Azkaban the film series reached a pinnacle in special effects, marked by the centerpiece of Harry riding Buckbeak the Hippogriff and flying around the Hogwarts castle. It's truly a fantastic and exhilarating sight that matches the grandeur of Bastian's flight with Falkor in The NeverEnding Story (1984) yet with a level of believability which had only recently been accomplished with special effects in cinema. From this point onward (circa 2004), the Harry Potter movies were right up there with the best of contemporary Hollywood in terms of CGI effect shots and even held their own against the likes of Star Wars Episode III: Revenge of the Sith (2005). The effect of Aunt Marge being blown up is quite impressive, and CG is put to good use with the phantom-like Dementors and transformations of animagi Sirius Black and Peter Pettigrew and lycanthrope Professor Lupin. The werewolf transformation in particular is executed well and the animation is convincing, even if the design of the wolf is a bit underwhelming. The look they went with here makes for an incongruent comparison to Fenrir Greyback in the later films but serves well enough in all practical respects.
On top of everything else it does well, the aspect that puts Prisoner of Azkaban over the top and solidifies it as one of the best Harry Potter films is its screenplay. Faced with adapting the first of J.K. Rowling's novels which was over 400 pages in length (as compared to the approximate 300 pages of the preceding novels), Steve Kloves turned out his best screenplay of the seven Harry Potter scripts he wrote and adeptly trimmed down the tightly packed third book; Harry Potter and the Prisoner of Azkaban runs 2 hours 21 minutes which is about 15-30 minutes shorter than the previous two films. A strong adaptation doesn't need to incorporate every event from a novel so much as it should capture the spirit of the story and communicate the most essential parts, and that's precisely what was accomplished here. The Fidelius charm, the elaborate backstory of Moony, Wormtail, Padfoot, and Prongs, how exactly Sirius broke out of Azkaban, and an extra trip to Hogsmeade and couple of Quidditch matches are excluded from the film, but these omitted details are hard to notice because the movie feels complete in terms of Year 3's plot, Hogwarts atmosphere, and character development. It's a real accomplishment as almost half the runtime is dedicated to the finale, given the multiple times the viewer witnesses the night of the full moon and the scheduled executions of Buckbeak and Sirius Black, thanks to the time turner.
In the context of Harry Potter and Prisoner of Azkaban, the time turner is a great plot device. In the greater context of the Harry Potter wizarding world, however, the time turner is a gaping plot hole. Under scrutiny, too many questions arise at its mere existence. Why would the Ministry of Magic grant a 13 year old witch access to use a time turner so she can learn about Divination and Muggles? Why doesn't anyone use the time turner for other causes to bring about justice or better society? What about all of the inevitable ripple effects caused by going back in time? If the story the audience is told features the mysterious stag patronus the first time we see the final night, isn't this technically a Beta timeline and not the true story of the original Alpha dimension Harry Potter?
Predestination (2014) is a masterful exposé of the ouroboros, a cinematic visualization of the ancient serpent which consumes its own tail. The Terminator series which began with 1984's The Terminator is a convoluted trainwreck with each subsequent sequel reestablishing the timeline but a fully-loaded franchise that successfully fuses action and sci-fi. In each of these examples, time travel is central, and any hypothetical scientific questions raised are inherent in the story being told; in other words, time travel is the main course. With Harry Potter, fans are served an antagonistic side dish of time travel alongside their high/low fantasy (depending on one's school of thought), coming of age entrée. The Harry Potter series needed time travel like a fish needs a bicycle.
J.K. Rowling knew introducing time travel was a risky idea but wrote it anyway, later backpedalling in hopes of quelling the silent "what if?"s and "why not?"s in every logical reader's mind but this only amplified the blunder and raised more loose ends later in the series. In the fifth novel, Harry Potter and the Order of the Phoenix, the reader is treated to the following absurdity (summary compliments to the Harry Potter wikia):
The entire stock of Time-Turners, located in the Time Room, in the Ministry of Magic were rendered useless during the Battle of the Department of Mysteries in 1996. While not "destroyed" per se, due to the way one of them fell when their counter was knocked over, the entire stock was trapped in an endless loop of falling over, un-falling, and then re-falling, in an endless cycle for all eternity, and are thus unable to be used.
What a crock of shit. And the parasitic stage production Harry Potter and the Cursed Child reopened the can of worms again in 2016. If J.K. simply never referenced the time turner subsequent to the publishing of Prisoner of Azkaban it wouldn't have been as problematic; the time turner could have blended in with the inclusion of other unique wizardly contraptions such as the marauder's map and deluminator. Thankfully the movie adaptations of Harry Potter were wise enough to leave well enough alone and never mention the time turner again in later films.
Back in the drafting of her third novel, J.K. Rowling had a good idea for a one-off story involving time travel that beautifully depicts Harry's character development and how he found inner strength amidst self-doubt by conjuring an immense patronus charm to save his past self, Hermione, and Sirius Black from a descending onslaught of Dementors. After long hours of struggling with this particular spell throughout the school year, Harry knew he could successfully cast the patronus charm when it mattered most because he knew his future self had already done it. While this time-travel-related character piece isn't as emotionally powerful as the Star Trek: Deep Space Nine episode "The Visitor" (1995) and doesn't mesh as well with its respective series' genre, Harry Potter and the Prisoner of Azkaban is still quite moving, so long as one can suspend his or her disbelief that little bit further.