I'm curious if JK Rowling has ever contradicted the books in an interview or a tweet.
Does anyone know of any examples of her directly contradicting known Harry Potter canon?
The tweet calling Harry Potter and the Cursed Child canon, though I believe HP:CC directly contradicts HP canon, does not count as an answer, as that was indirect.
When answering a question about wizards education before Hogwarts on her old website, JKR refers to Harry as a Muggle-born, defined as the wizard child of two Muggles.
What education do the children of wizards have before going to Hogwarts?
They are, as many of you have guessed, most often home educated. With very young children, as you glimpsed at the wizards' camp before the Quidditch World Cup in 'Goblet of Fire', there is the constant danger that they will use magic, whether inadvertently or deliberately; they cannot be trusted to keep their true abilities hidden. Even Muggle-borns like Harry attract a certain amount of unwelcome attention at Muggle schools by re-growing their hair overnight and so on.
- F.A.Q. on JKR’s old website
Of course, while he grew up with the Muggle family of the Dursleys, his mother was a witch and his father was a wizard.
“Now, yer mum an’ dad were as good a witch an’ wizard as I ever knew. Head Boy an’ Girl at Hogwarts in their day!”
- Harry Potter and the Philosopher's Stone, Chapter 4 (The Keeper of the Keys)
Harry was most certainly not a Muggle-born.
When answering questions about the first Fantastic Beasts movie, JKR states that the reason Newt could not summon all his creatures with Accio is that Accio only works on inanimate objects and causes them to travel at nearly the speed of light.
3. Why couldn’t Newt use ‘Accio’ to retrieve all his beasts?
‘Accio’ only works on inanimate objects. While people or creatures may be indirectly moved by ‘Accio-ing’ objects that they are wearing or holding, this carries all kinds of risks because of the likelihood of injury to the person or beast attached to an object travelling at close to the speed of light.
- Welcome to my new website! (J.K. Rowling’s new website)
However, it consistently is shown in the Harry Potter books that objects that are summoned by Accio can be seen flying towards the wizard who Summoned them and caught without causing injury. Objects traveling at the speed of light are invisible, and would injure anyone attempting to catch them.
“Mrs Weasley pointed her wand at George’s pocket and said, ‘Accio!’
Several small, brightly coloured objects zoomed out of George’s pocket; he made a grab for them but missed, and they sped right into Mrs Weasley’s outstretched hand.”
- Harry Potter and the Goblet of Fire, Chapter 6 (The Portkey)
Accio is always shown to work on animals as well as objects, with no harmful effects to the animal in question.
“I’m almost certain of it,’ said Hermione grimly. ‘Watch your frog, it’s escaping.’
Harry pointed his wand at the bullfrog that had been hopping hopefully towards the other side of the table – ‘Accio!’ – and it zoomed gloomily back into his hand.”
- Harry Potter and the Order of the Phoenix, Chapter 18 (Dumbledore’s Army)
This is also true in the Fantastic Beasts series. In “Fantastic Beasts and Where to Find Them”, the movie which her statement was about, Newt does summon one of his creatures with Accio.
“The Niffler is still only for a moment before running off down the street. Newt quickly gathers himself, drawing his wand:
NEWT
ACCIO!In slow motion the Niffler sails backward through the air toward Newt. As he flies, he looks sideways at the most glorious window display yet. His eyes widen. Jewelry falls from his pouch, flying toward Newt and Jacob, who duck and dive as they run forward toward the creature.”
- Fantastic Beasts and Where to Find Them (The Original Screenplay)
He does this a second time in the sequel.
NEWT
Accio Niffler!The case bursts open and a Niffler jumps out.
NEWT
Get looking.NEWT climbs onto the case and inspects impressions of creatures revealed in the air, while the now-trained adult Niffler sniffs out clues.
- Fantastic Beasts: The Crimes of Grindelwald (The Original Screenplay)
Her statement that Newt could not summon any of his creatures with Accio is contradicted even further by the fact that not only is it theoretically possible, on two separate occasions Newt did exactly that.
In “Harry Potter and the Philosopher’s Stone”, Quirrell was possessed by the Dark Lord after he failed to get the Stone from Gringotts, so the Dark Lord decided to watch him more closely.
“Since then, I have served him faithfully, although I have let him down many times. He has had to be very hard on me.’ Quirrell shivered suddenly. ‘He does not forgive mistakes easily. When I failed to steal the Stone from Gringotts, he was most displeased. He punished me … decided he would have to keep a closer watch on me …”
- Harry Potter and the Philosopher's Stone, Chapter 17 (The Man with Two Faces)
In “Harry Potter and the Goblet of Fire”, Voldemort also stated that he only took possession of Quirrell’s body a while after encountering him.
“A wizard – young, foolish and gullible – wandered across my path in the forest I had made my home. Oh, he seemed the very chance I had been dreaming of … for he was a teacher at Dumbledore’s school … he was easy to bend to my will … he brought me back to this country, and after a while, I took possession of his body, to supervise him closely as he carried out my orders.”
- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)
However, in the Pottermore writing, J.K. Rowling says that the Dark Lord possesses Quirrell immediately upon encountering him and realizing he taught at Hogwarts, instead of after he was already serving the Dark Lord but failed to get him the Philosopher’s Stone.
Though Hagrid was correct in saying that Quirrell had a ‘brilliant mind’, the Hogwarts teacher was both naive and arrogant in thinking that he would be able to control an encounter with Voldemort, even in the Dark wizard’s weakened state. When Voldemort realised that the young man had a position at Hogwarts, he took immediate possession of Quirrell, who was incapable of resisting.
- Professor Quirrell (Pottermore)
This is a clear contradiction of what is stated in the books.
In the Pottermore writing on Professor McGonagall, JKR claimed that her Hogwarts letter arrived on her eleventh birthday.
Minerva never forgot how much her mother cried, when the letter of admittance into Hogwarts School of Witchcraft and Wizardry arrived on Minerva’s eleventh birthday; she knew that Isobel was sobbing, not only out of pride, but also out of envy.
- Professor McGonagall (Wizarding World website)
However, Harry’s Hogwarts letters start arriving several days before his birthday - the Dursleys had time to change his bedroom, go to a hotel, and hide in a hut in an attempt to hide from the letters. July 31st was also coincidentally the deadline to reply, when Hagrid had to make sure to get to Harry by.
*“Dear Mr Potter,
We are pleased to inform you that you have a place at Hogwarts School of Witchcraft and Wizardry. Please find enclosed a list of all necessary books and equipment.
Term begins on 1 September. We await your owl by no later than 31 July.”*
- Harry Potter and the Philosopher's Stone, Chapter 4 (The Keeper of the Keys)
As soon as Hagrid finds him, he sends off a reply to the owl.
“With his tongue between his teeth he scribbled a note which Harry could read upside-down: Dear Mr Dumbledore,
Given Harry his letter. Taking him to buy his things tomorrow.
Weather’s horrible. Hope you’re well.
Hagrid”
- Harry Potter and the Philosopher's Stone, Chapter 4 (The Keeper of the Keys)
Therefore, from the books, the deadline for all students to respond to their Hogwarts letters seems to just coincidentally fall on Harry’s birthday. Additionally, in another Pottermore writing, JKR states that no letter arrived for Angus Buchanan when he was due to leave for Hogwarts, and never mentioned him not receiving one on his birthday specifically.
The deception was innocently begun, but as the time approached for him to leave for Hogwarts, Angus and his siblings became uneasily aware that they could not maintain the pretence much longer. No letter from school arrived for Angus, but his panicking sister Flora forged one, which kept the parents in ignorance for several weeks more.
- Scottish Rugby (Wizarding World website)
Also, since Angus was born in the mid-nineteenth century, that eliminates the possibility of it being a rule change after McGonagall’s Hogwarts years.
In an interview in 2005, two years before the final book, J.K. Rowling says that Grindelwald is dead.
ES: Our other “Ask Jo” question (the one about James and Lily’s sacrifices), was from Maria Vlasiou, who is 25, of the Netherlands. And then the third is from Helen Poole, 18, from Thirsk, Yorkshire – also one of the “Plot Thickens” fan book authors. It’s the one about Grindelwald, which I’m sure you’ve been gearing up for us to ask.
JKR: Uh huh.
ES: Clearly -
JKR: Come on then, remind me. Is he dead?
ES: Yeah, is he dead?
JKR: Yeah, he is.
- Leaky Cauldron interview (16 July, 2005)
However, in the seventh book, he’s shown to be alive, until Voldemort kills him. In this case, she was wrong about something that wasn’t published yet. (I’ll look for other examples and update).
In Quidditch Through the Ages, it’s mentioned that Peru is likely to be the first Latin American country to win the Quidditch World Cup, meaning none had won yet when this was published.
“Argentina and Brazil both reached the quarter-finals of the World Cup in the last century. Undoubtedly the most skilled Quidditch nation in South America is Peru, which is tipped to become the first Latin World Cup winner within ten years.”
- Quidditch Through the Ages
Quidditch Through the Ages is up to date to at least 1994, since it mentions a game played that year, so it can’t possibly have been written and not updated with new content since before 1994.
“The exception to this general rule is Japan, where Quidditch has been gaining steadily in popularity over the last century. The most successful Japanese team, the Toyohashi Tengu, narrowly missed a win over Lithuania’s Gorodok Gargoyles in 1994.”
- Quidditch Through the Ages
However, in the Quidditch World Cup writings J.K. Rowling published on Pottermore, she says the Brazilian team won the Quidditch World Cup five times, while also saying that the time that could theoretically be accounted for by Quidditch Through the Ages being published before it happened, since it’s at least as current as 1994, was when they weren’t playing well and having bad years.
Brazil has won the Quidditch World Cup five times, but the nineties and early noughties were generally considered wilderness years for this once great side. Manager José Barboza has reinvigorated the national game, bringing in younger players from every corner of the country. With an average age of only 22, this is the least experienced side remaining in the tournament.
- Quidditch World Cup 2014: Daily Prophet Reports (Pottermore)
