Harry Potter have several examples of Early-Installment Weirdness.
- The rules of magic seem to have not been quite worked out in the first book. Several spells are performed nonverbally and without wands, both of which are established to be difficult in later books. Hagrid, despite having been expelled in his third year, is able to perform nonverbal spells, something which the main characters wouldn't learn until their sixth year (it is possible he picked that up later, but it would be still a big feat for such an inept wizard like Hagrid). He also successfully performs magic with a broken wand, something that the second book establishes as near-impossiblenote . Ron also unsuccessfully tries to perform a spell by reciting a rhyming couplet, even though (being raised in a Pureblood family) he should know that magic incantations are short phrases and usually in Latin. Apart from the levitation spell and alohomora, specific spells, their incantations, and their specific effects are not really brought up in the first book.
- Harry Potter and the Philosopher's Stone:
- The first chapter uses a classic third-person omniscient style of narration, starting in Vernon Dursley's head before casually switching, around mid-chapter, to the point of view of Professor McGonagall in her Animagus form. Later in the book it briefly switches to Ron's and Hermione's perspective during the first Quidditch match, and there are occasional other points early on that momentarily dip away from Harry's perspective (as when it observes that Harry forgot what he dreamed about the previous night). Most of the series, however, is told strictly from Harry’s point of view. Some of the later books feature an opening chapter from another character’s viewpoint, but even these use strict third-person limited narration.
- Draco challenges Harry to a duel. He and Ron treat the prospect as being like a gun duel, with an arranged time and place, and Ron and Goyle serving as seconds. From the second book onwards, duelling just refers to fighting with magic, and the only formality associated with it is when Voldemort mockingly makes Harry bow to him in Goblet of Fire.
- Harry is dismayed to have lost "two points for Gryffindor in his very first week", both of which Professor Snape deducts in Harry's first Potions class. This seems to make sense, as McGonagall later takes five from Hermione for supposedly putting herself in danger, Harry is awarded sixty points for defeating Voldemort, and scores for each House at the end of the year (none of which are multiples of five) are only a few hundred each. However, points in general seem to undergo inflation as the series goes on. On all subsequent occasions teachers take or give five or ten at a time. It seems strange that preventing the most dangerous dark wizard of all time from returning to power is only worth six times as much as answering a question right in class.
- Similar inflation occurs with wizard currency. In Philosopher's Stone, Harry buys his wand for seven Galleons (and it's established that each wand is unique and creates a bond with its owner), but in Half-Blood Prince a simple copy of a schoolbook costs nine Galleons.
- In Ron's introduction, he says that his entire family are magic except for one of his mother's second cousins, who's an accountant (thereby implying he's a Squib), but Ron says they never talk about him. As we get to know the Weasleys, it seems increasingly odd that they would ignore this relative, especially with how interested Arthur Weasley is in Muggles.
- The attempt to kill Harry by knocking him off his broom mid-Quidditch match is hard to take seriously after reading the following books, in which Harry gets successfully knocked out mid-flight several times and securing his landing is always rather trivial. For those keeping count, that means Cormac McLaggen came closer to killing Harry than Quirrell did.
- Some of McGonagall's early behaviour, such as reading a map in cat form openly long enough for Vernon to see her doing so, is very uncharacteristic for her in later books — and a little hypocritical, given that she complains to Dumbledore only a few hours later that, by flamboyantly celebrating Voldemort's demise, wizards are risking the exposure of their community.
- The American edition changes most British English terms to American ones. For example, "mom" is used instead of "mum," and it's mentioned that Dean Thomas is a "soccer" fan. After the first book turned out to be a massive hit in the United States, Rowling was successfully able to convince Scholastic to keep British terms and phrases in future installments (with the exception of references to the Philosopher's Stone, which is still called the "Sorcerer's Stone" for continuity purposes).
- The school song is sung at the first dinner after Harry and the gang are sorted, then never again following the Sorting Ceremony in any subsequent year. Rowling has explained it away as Dumbledore only having it sung when he's feeling particularly cheerful.
- The reason Dumbledore can't help Harry during the finale is that he is travelling to the Ministry via broom. There is never any suggestion again of wizards travelling long distances on broom, as later books reveal that all Hogwarts students learn to Apparate (i.e., teleport) as part of the school curriculum. Later books also introduce Floo powder (magical powder that allows wizards to instantaneously travel to distant buildings via the fireplace) and Portkeys (objects that teleport those who touch them between fixed places.)
- Voldemort and his followers are implied to be motivated entirely by desire for power, with Voldemort's Evil Plan revolving around his quest to become immortal (appropriate, given that his name means "Escape from death" in French). While there are a few hints that some wizards don't like Muggle-borns (for example: upon first meeting Harry, Malfoy bluntly asks him whether his deceased parents were wizards), it isn't established until the next book that another major motivation for Voldemort's followers is Fantastic Racism against wizards with Muggle ancestry; Voldemort's quest for immortality didn't re-enter the picture until the last two installments, finally bringing that aspect of the character full-circle.
- Harry Potter and the Chamber of Secrets:
- Tom Riddle mentions that Hagrid was raising werewolf cubs under his bed. In the very next book, it becomes clear that werewolves are humans afflicted with a disease that makes them become wolves during a full moon. JKR later wrote
that the Forbidden Forest is home to a pack of unusually intelligent wolves resulting from two transformed werewolves mating, likely to explain this and Ron's comment in the first book that there were werewolves in the forest. Perhaps as a callback to this, in the seventh book, Voldemort refers to the hypothetical offspring of an heroic werewolf as "cubs", in a context that makes it clear that he's making a rather offensive joke. - The book implies (through Lockhart stealing real people's accomplishments and not just making them up) that there is a charm that can cure lycanthropy. Lupin's backstory in the later books establishes this is definitely not the case: once bitten, a person remains a werewolf for life, and can only use certain methods to control their transformation to avoid hurting others.
- Tom Riddle mentions that Hagrid was raising werewolf cubs under his bed. In the very next book, it becomes clear that werewolves are humans afflicted with a disease that makes them become wolves during a full moon. JKR later wrote
- Harry Potter and the Prisoner of Azkaban refers to Hit Wizards, whose role is replaced by Aurors. At one point in the first book, Harry refers to "going over to the Dark Side" (obviously in the context of refusing ever to do such a thing). It's not until Goblet of Fire that we learn that Voldemort's supporters are called Death Eaters and that Ministry of Magic employees who hunt dangerous wizards are called Aurors (later materials establish Aurors and Hit Wizards to be different jobs, with the former being akin to FBI and the latter being more in the line of SWAT teams).
- Harry Potter and the Goblet of Fire:
- Rowling hadn't quite nailed down how Harry's mental connection to Voldemort worked when it first appeared. Harry's vision was apparently in third person, following Frank Bryce, who stumbled on Voldemort and Pettigrew's hiding place. He even sees Voldemort's current form from Bryce's POV, though he can't remember it upon waking up. Starting in Order of the Phoenix, all his Voldemort visions are seen through the eyes of Voldemort himself, with the narration speaking as though Harry himself were committing the actions Voldemort commits.
- Goblet of Fire has the first mention of splinching, in which someone trying to Apparate accidentally leaves part of themselves behind. According to Mr. Weasley, the two involved were fine, just unable to move until the Accidental Magic Reversal Squad arrived to free them — suggesting that it's like getting Stuck in the Doorway, except that in this case it's a door through reality. In later books, however, we actually see cases of splinching, and it's... pretty much what you'd expect.
- Terminology is confused several times in early books. In the first book, Neville mentions that his family was worried he'd turn out to be a Muggle, i.e. not have any magic, but from the second book onwards, non-magical individuals born to magic parents are called Squibs.
- In a non-continuity-related example, J. K. Rowling's writing style becomes more florid over the course of the series, while the tone becomes much less kooky and whimsical, with the series gradually replacing more and more of its Roald Dahl-style bounce with sturm und drang as it goes along. As an example: in trying to get away from the constant owl post deliveries, Vernon moves his family and Harry to a rickety cabin perched on a rock in the middle of the sea—an abrupt change of scenery that wouldn't be out of place in James and the Giant Peach. After Hagrid tracks them down, this cabin is never mentioned again. This is apparently because Vernon thought wizards couldn't cross running water.
- Snape's introductory statement that there "will be little foolish wand-waving" in the class implies that there is some sort of disciplinary rivalry between potion making and wand-based magic, but this is never elaborated on. The two areas of magic are shown to be mutually complementary, with good potion makers uniformly depicted as being expert spells-casters as well. Indeed, Snape himself is no slouch with a wand and would rather be teaching Defense Against the Dark Arts, a class which uses a lot of wand spells and not much potion-making.
- Apparition is first treated as very dangerous, and something that few wizards would do. By Book 6, Apparition is quite ubiquitous and most characters use it freely. A course is even taught to 6th year students, serving as a rite of passage for soon to be adult wizards, akin to real life's driver's licence. Although, much like driving, it's not without its dangers.
