In the book, Harry breaks his right arm, but in the illustration by Mary GrandPré, his left arm has been broken.
The first edition of the book has Dumbledore incorrectly identify Voldemort as "the last remaining ancestor of Salazar Slytherin". Later editions change this to "last remaining descendant".
Working Title: Harry Potter and the Half-Blood Prince. J. K. Rowling's comments on this imply she had originally intended to use the Half-Blood Prince's entire plotline in the second book, but moved it back when she found it didn't fit very well into that book's plot.
Write Who You Hate: JK Rowling once mentioned at the Edinburgh Book Festival 2004 that Professor Gilderoy Lockhart is the only character in the work based on a real personnote she insists it's not her ex-husband who she claims is an enormous blowhard just like him, and that she barely exaggerated his real personality; even if she dropped hints, she refused to comment on who, because she didn't want to give him the satisfaction.
J.K. Rowling: The only character who is deliberately based on a real person is Gilderoy Lockhart. Maybe he is not the one that you would think of, but I have to say that the living model was worse. He was a shocker! The lies that he told about adventures that he'd had, things he'd done and impressive acts that he had committed... He was a shocking man. I can say this quite freely because he will never in a million years dream that he is Gilderoy Lockhart. I am always frightened that he is going to turn up one day. He is just one of those people from your past whom you feel you have never quite shaken off. I will look up one day at a signing and he will say, "Hello, Jo". Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.
The Film Adaptation
Ability over Appearance: The casting call for Tom Riddle insisted on actors aged 15-17. Christian Coulson, who was 23, gave the best audition and was cast. He did not, however, reprise the role for the sixth film, being deemed too old by that time.
In addition to the sets at Leavesden Studios, Hogwarts was represented in this film by Alnwick Castle, Durham Cathedral, Gloucester Cathedral, Lacock Abbey, and Oxford University. All of these locations carried over from the first movie, but some of them would not last beyond this one as the third movie would transition to filming most of the Hogwarts interiors at the studio. They would return to Oxford for the fourth and sixth movies, Gloucester Cathedral for the sixth movie, and Lacock Abbey for Fantastic Beasts: The Crimes of Grindelwald, but Alnwick Castle and Durham Cathedral never appear in the series again after Chamber of Secrets.
While the interior of King's Cross was shot at the real King's Cross, the exterior is represented by the more visually impressive St. Pancras Station, which is located nearby. This recurs in Deathly Hallows, Part 2, which opens the epilogue with an Establishing Shot of St. Pancras.
A personal letter from David Heyman to Alan Rickman following the production of this movie reveals that the actor was occasionally frustrated with the role. This is not particularly surprising if you remember that Snape has a limited role in this particular movie.
Screenwriter Steve Kloves disliked the Slow Clap scene at the end of the film, feeling that it was inauthentic. Apparently, the scene was the idea of Chris Columbus, who thought it would make for a good moment to end on.
The three main actors dislike watching their performances in this film, along with the first one, as they consider their later appearances to be much better in comparison.
As noted above, Christian Coulson was 23 playing 16. Likewise, Shirley Henderson, who plays school-age Myrtle, was 37.
Robbie Coltrane portrays both his current-day and teenage versions, with his younger self distinguished by being clean-shaven with shorter hair. Him appearing much older than he actually was could be explained through his giant anatomy, though.
Edward Tudor Pole had a scene as Mr Borgin that was cut from the final film but included as an extra on the DVD. The scene was also restored for the extended cut.
Sally Montemor was cast as Madam Pince the librarian but her scenes were cut. She's seen in the background in the library and at the staff table during dinner.
Deleted Scene: Bonnie Wright revealed that she filmed a scene in which Ginny strangles roosters outside of Hagrid's hut. In the book, it was revealed that Ginny, under Tom Riddle's influence, killed Hagrid's roosters, since the crow of roosters is fatal to the basilisk. This fact is entirely omitted from the movie, therefore the scene was cut. Presumably, it would have been one of the flashbacks that appear during Riddle's Evil Gloating.
Duelling Movies: In a repeat of their respective previous installments' duel the previous year, the film came out one month before the movie of The Lord of the Rings: The Two Towers. As before, the outcome was pretty much a tie and both were massive box office hits. To date, this is the last time the two franchises have competed at the box office. The Rings trilogy concluded in 2003 while the third Potter film came out in 2004, and the trilogy of The Hobbit was released between Deathly Hallows, Part 2 and Fantastic Beasts and Where to Find Them.
In the scene where Harry meets Mr. Weasley and the latter asks him a question about Muggles, Mark Williams ad-libbed a different Muggle object in each take (the final cut's being a rubber duck) so that Daniel Radcliffe would actually be caught off guard by the question.
Rupert Grint has such a severe case of arachnophobia, he had trouble watching the entire scene where Ron and Harry are in Aragog's hollow. In that scene, Ron's frightened look, and his uncomfortable squirming throughout, was not from acting, but from Rupert being legitimately terrified at even the thought of spiders.
Jason Isaacs said in the 20th Anniversary reunion special that in a deleted scene taking place in Borgin & Burkes, Lucius smacks Draco's hand with the snake-head on his Classy Cane and scolds Draco to not touch anything. Unbeknownst to Isaacs, the snake-head had little sharp fangs, and they punctured Tom Felton's hand. Isaacs immediately broke character to apologize profusely to a tearful Felton, who replied through his tears, "it's alright, it's good for the scene..."
On the first day I came down for breakfast, Richard Harris was having his toast and marmalade at another table with Maggie Smith. I said to him, brightly, "Good morning", and he growled, "Fuck off". I didn't know that he had leukaemia, so I was quite offended at the time. I kept myself to myself after that, at least where Dumbledore was concerned.
For when Harry and Ron are using Polyjuice to impersonate Crabbe and Goyle, Jamie Waylett and Joshua Herdman play them on-set, then Daniel Radcliffe and Rupert Grint re-recorded their dialogue during post-production.
Missing Trailer Scene: The theatrical trailer includes shots of Crabbe and Goyle being hidden in a broom cupboard and of the Ford Angelia nearly flying into the St. Pancras Clock Tower. These shots were deleted from the theatrical cut of the movie, but they were added back in for the extended cut.
A minor example at the end. Hermione was down in the script to hug Harry and Ron, but Emma Watson was too embarrassed to hug both boys in front of a set full of people (it's in the Great Hall). They came up with the compromise that she would only hug Harry and give Ron an awkward handshake. In post-production, they even had to slow down the film when Hermione is hugging Harry. Emma kept breaking it too quickly.
On the animal side of the equation, the scene with all the animals in McGonagall's class had a problem with a mandrill who wouldn't stop masturbating. This mandrill's naughtiness even made it into the completed film, albeit in the background and only for a couple seconds.
Sort of. Madam Pomfrey only appeared in the background of the first film, played by an extra. Here Gemma Jones assumes the role and keeps it for the remainder of the series.
There were some changes in the cast of the Latin American Spanish dub due to it being made in a different studio, such as Víctor Hugo Aguilar replacing Humberto Solórzano as Hagrid, or Keta Leonel replacing Magda Giner as the permanent voice for McGonagall. Carlos Segundo (Professor Snape) and Arturo Castañeda (Harry) also left because of disagreements with their salaries, and were replaced by Rolando de Castro and Claudio Velázquez, respectively.
Posthumous Credit: Richard Harris managed to complete all of his scenes before he succumbed to Hodgkin's disease on 25 October 2002 a few days before the premiere.
Real-Life Relative: All four of Chris Columbus's children appear in this movie. Eleanor Columbus plays Susan Bones (she also played her in the first movie), Brendan Columbus played a boy in study hall, Violet Columbus played the little girl with flowers, and Isabella Columbus played the little girl in the bookstore.
Lucius attempting Avada Kedavra on Harry was ad-libbed by Jason Isaacs. At this point, he had only read the fourth book and that was the only spell he could remember. Additionally, Isaacs had to keep his head tilted back to prevent the long blond hair from falling in front of his face, which helped make Lucius appear even more haughty and snobby. He even improvised kicking Dobby; he lost track of where he was supposed to look during filming, to which Chris Columbus told him to look anywhere and the effects team would put Dobby there. He added in the kick for good measure, and Columbus initially thought he was slipping before Isaacs explained it.
Jason Isaacs also ad-libbed his famous remark to Harry in Dumbledore's office, as he felt it fit Lucius's character to always try to get the last word in. To his surprise, Daniel Radcliffe then improvised Harry’s equally iconic response.
Lucius: Let us hope that Mr. Potter will always be around to save the day.
Harry: Don’t worry. I will be.
Hermione was supposed to hug both Harry and Ron at the end, but Emma Watson was too embarrassed to hug both boys in front of a crowd of people. Thus came the compromise where she hugs Harry but only shakes Ron's hand. It ended up as an accidental foreshadowing of their future relationship (which didn't get hinted at until the fourth book). What's more is that the film had to be frozen for a few seconds because Emma kept breaking the hug too quickly.
Draco Malfoy's "I didn't know you could read" line to Harry-as-Goyle was ad-libbed by Tom Felton, who had forgotten his lines.
Draco grumpily dragging Crabbe down when he stands up with the rest of the students to applaud Hagrid's return was a result of Crabbe's actor, Jamie Waylett, forgetting that he wasn't supposed to stand up and join in.
Voiced Differently in the Dub: During the film, it was noticeable that both Daniel Radcliffe and Rupert Grint were going through puberty, so their voices sound a bit deeper than in Philosopher's Stone. But for some reason, the Latin American Spanish dub decided to keep Harry and Ron sounding like younger kids, with Harry even getting another child voice actor to do his voice in the movie. Fortunately, by Prisioner of Azkaban, their voices were finally recast with older voice actors to match the English ones.
You Sound Familiar: Two retroactive examples in the Brazilian dub: Hamilton Ricardo played the Bazilisk's voice, and would reappear from the next movie on as Lupin, and Luiz Carlos Persy, who voiced Aragog, would be cast later as Voldemort.
The PC version has a hidden challenge level in the Gryffindor common room that can only be accessed by enabling the debug mode. There's also code for a minigame where the player would fly the Ford Anglia to Hogwarts at the beginning of the game and a meter with an eye that would apparently fill up as muggles noticed the car. It was scrapped and replaced with a cutscene, seemingly before a level was designed for it.
The Game Boy Color version has three enemies that don't appear in any area of the game. The Doxy Queen, Emerald Firecrab, and Dark Goblin all have Folio Bruti entries, but aren't programmed to appear in any encounters.
Executive Meddling: The developers of the PC version wanted to make it so that the other houses could win at the end, but the EA executives forced them to rig it so that only Gryffindor could get the House Cup. The final Chamber of Secrets level was also much more elaborate with difficult puzzles and enemies, but the producers demanded it be simplified to running past fire-breathing snake statues because they thought the original idea was too hard for kids.
The Other Darrin: Some of the voice actors from the first game have been replaced:
Tom Attenborough (grandson of Richard) replaces Joe Sowerbutts as Harry.
Lewis MacLeod replaces Joe Sowerbutts as Draco, David de Keyser as Dumbledore, and Gregg Chillin as the Weasley twins. Chillin does, however, continue to voice Ron.
Gary Fairhall replaces Harry Robinson as Neville.
Two Voices, One Character: In the PS1 game, Quidditch commentator Lee Jordan ends up having two different voices between the main game and the Quidditch League side mode. In the main game, he has the younger-sounding voice he had in the first game, while Quidditch League gives him a deeper voice more in line with the film’s depiction. This comes as particularly odd due to Quidditch League reusing the commentary from the first game wholesale, while the main game is almost entirely new lines.
that Professor Gilderoy Lockhart is the only character in the work based on a real personnote who she claims is an enormous blowhard just like him, and that she barely exaggerated his real personality; even if she dropped hints, she refused to comment on who, because she didn't want to give him the satisfaction.J.K. Rowling: The only character who is deliberately based on a real person is Gilderoy Lockhart. Maybe he is not the one that you would think of, but I have to say that the living model was worse. He was a shocker! The lies that he told about adventures that he'd had, things he'd done and impressive acts that he had committed... He was a shocking man. I can say this quite freely because he will never in a million years dream that he is Gilderoy Lockhart. I am always frightened that he is going to turn up one day. He is just one of those people from your past whom you feel you have never quite shaken off. I will look up one day at a signing and he will say, "Hello, Jo". Other people have contributed the odd characteristic, such as a nose, to a character, but the only character who I sat down and thought that I would base on someone is Gilderoy Lockhart. It made up for having to endure him for two solid years.