History Film / HarryPotterAndTheHalfBloodPrince

** In the book, there is a subplot in which Harry, Ron, and Hermione have a falling out with Hagrid as he’s upset they were forced to drop his class for their sixth year of studies. They grow cold and distant from each other and eventually hostile, but eventually reconcile when Hagrid reveals that he fears that Aragog is dying, and realizes that they didn’t drop his class due to not liking him anymore.
In the film, Hagrid is only seen in the background, if at all, between taking Katie to the castle and Aragog's funeral, and no mention of Aragog, his health or otherwise, is made prior to his death.

** In the book, Harry, Hermione, and Ron had seen very little of Hagrid for some time. He had not been attending meals, and was not seen around the school very much, and whenever they did see Hagrid, he would fail to acknowledge them. Finally, the three visit Hagrid at his hut, and notice he has a barrel of foot-long maggots, which he tells them is food for Aragog. Hagrid goes on to tell Harry, Hermione, and Ron that Aragog got sick over the summer and was not getting any better, and Hagrid fears Aragog may be dying. In the film, Hagrid is only seen in the background, if at all, between taking Katie to the castle and Aragog's funeral, and no mention of Aragog, his health or otherwise, is made prior to his death.

** At the midpoint of the film, the Death Eaters attack and burn down the Burrow, in a scene not in the books. The filmmakers added this to add a perilous beat for the characters in a second act that didn't have one otherwise, rather than the characters reading about the Death Eaters' menace in the ''Prophet'' as in the novel.

** At the midpoint of the film, the Death Eaters attack and burn down the Burrow, in a scene not in the books.

** Draco's efforts in the Room of Requirement are shown much earlier in the film for the sake of DramaticIrony - including using an apple and two birds to test [[spoiler: the Vanishing Cabinet]].

** The scene with Fudge catching up the Muggle Prime Minister on what’s going on in the Wizarding World is absent.

* ADeathInTheLimelight: [[spoiler:Michael Gambon as Dumbledore gets the largest presence in the movies and its promotion (see the above poster) as befitting his final living role in the series.]]

''Harry Potter and the Half-Blood Prince'' is the sixth ''Film/HarryPotter'' film, released in 2009.

* TrappedWithTheTherapySession: Harry and Ron are in a train compartment together when Lavender, Ron's girlfriend, comes up and breathes on the glass pane of the door so she can draw a heart with her and Ron's initials. Harry starts examining his armrest as if he's never seen one before.
* VomitDiscretionShot: At one point, Cormac is shown leaning down out of camera shot and vomiting on Snape's shoes.

After ''Goblet of Fire'' and ''Order of the Phoenix'' began cutting plots and characters left and right to fit as movies, this film has an air of just going with it, and happily continues in the direction set by the films so far, cuts and all. While it may cause fans to nitpick (it's rather involuntary at this point), it's nevertheless easily one of the biggest fan-favorites of the series. Perhaps most notable is the major factor that the final book had been released by this film's premiere, allowing this film to begin some heavier foreshadowing of the next films since the writer finally knew how the story would end.

* CastingGag: Helen [=McCrory=] who plays Narcissa, was the original actress cast for Bellatrix - but she had to back out after getting pregnant. And her replacement (and on-screen sister) Creator/HelenaBonhamCarter was pregnant during production of this film.

* ScrewTheRulesIMakeThem: Dumbledore and Harry apparate, arriving ''within'' the Hogwarts grounds, something it was repeatedly pointed out in the books was impossible. Were it possible, Draco wouldn't have had to fiddle with a Vanishing Cabinet for months to get the Death Eaters in. But Dumbledore hints that there's a special exemption in the defensive barriers for the Headmaster:

* ADeathInTheLimelight: [[spoiler:Michael Gambon as Dumbledore gets the largest presence in the movies and its promotion (see the above poster) as befitting his final living role in the series.]]

[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/harrypotter6.png]]

* MoodWhiplash: Right after Slughorn cures Ron of Romilda's love potion, he, Ron and Harry attempt to have a drink together, which causes Ron to collapse. At first, it seems like a CrowningMomentOfFunny... until Ron starts spasming and nearly convulsing on the floor.

* AscendedExtra: Ginny, who goes from minor character to a rather vital person in Harry's life. A common complaint of the book is that this happens too much in a "tell, don't show" manner, so the film tries to temper this by giving her character more development (and more time around Harry).

** Subplots involving Ron's insecurity and Cormac [=MacLaggen=]'s bossiness were cut for time, leaving Ron without much of a character arc and Cormac as a mere DesignatedVillain.

* ActorAllusion:
** Whether intentional or not, Slughorn called Ron 'Rupert', a reference to Rupert Grint, who plays Ron in the movies.
** Creator/AlanRickman had a reaction like this when filming [[spoiler: Dumbledore's death scene]], since it wasn't the first time he'd been involved in someone being shot off [[Film/DieHard a high building]].

** Draco's efforts in the Room of Requirement are shown much earlier in the book for the sake of DramaticIrony - including using an apple and two birds to test [[spoiler: the Vanishing Cabinet]].

* DenserAndWackier: Downplayed, but the film has a lot more comedic moments and [[WorldOfSnark more snarking from all characters]]. The Felix Felicis scene is played much more for comedy than it is in the book. Some reviews even labelled the film a RomanticComedy. There are however plenty of serious moments (including introducing some tear jerker scenes that weren't in the book).

* ExpositoryHairstyleChange: Malfoy's hair shortening into a neater short, back and sides signals his transition into a more serious and conflicted character.

* AdaptationExpansion: Exclusive to the film is Slughorn's story about Francis, a fish Lily Evans made out of a lily petal as a student which she gave to Slughorn. He lost it 16 years ago, the very day Lily Potter was killed, a fact which makes Slughorn guilty enough to help Lily's son at the expense of his own security.

* ArtisticLicenseHistory: Despite being set in 1996-97, they manage to destroy the Millennium Bridge, which wasn't started until 1998.

* CreepyChild: Tom Riddle, but especially so in the movie (which works really well, seeing it's the nephew of the guy who plays him as an adult!). A good example - in both the book and the movie Dumbledore sets Tom's collection of trophies he's stolen from the other orphans on fire to both show him he's not lying and (attempt to) teach him a lesson. Book Tom's reaction to a bonfire erupting in his room is awed shock and a bit of fake apology. Movie's Tom's reaction is an ''undeniably giddy smile.'' <shudder>

* AdaptationExpansion: Exclusive to the film is Slughorn's story about Francis, a fish Lily Evans made out of a lily petal as a student which she gave to Slughorn. He lost it 16 years ago, the very day Lily Potter was killed, a fact which makes Slughorn guilty enough to help Lily's son at the expense of his own security.