1) Neville wasn’t to blame for doing poorly at Hogwarts
In the first 5 books, Neville is portrayed as a clumsy wizard, who can’t do spells right and is always getting confused. In The Order of the Phoenix, we receive some precious information when the wand breaks and the boy says that his grandmother will kill him for breaking his father’s wand.
It changes everything. As we know, in the Harry Potter universe, the wand chooses its owner. If the wand belonged to Neville’s father, then she didn’t choose him. When he gets a wand of his own from Ollivander, he becomes a first-class wizard.
In other words: Neville was never a bad wizard, it was just his wand that didn’t cooperate.
2) Sirius Black appears in the first book
JK Rowling already had the saga mapped out in her head when she wrote the first book and inserted a mention of Sirius Black that probably went unnoticed by a lot of people. Even because, at the time, it didn’t seem important.
Early in Philosopher’s Stone, Rubeus Hagrid goes to Privet Drive carrying baby Harry. He rides a flying motorbike and explains to Professor Dumbledore: “I borrowed it, sir. Young Sirius Black lent it to me.» We readers would only meet Black in the third book, The Prisoner of Azkaban.
3) Professor Trelawney spotted the Horcrux in Harry
Professor Trelawney, at the end of the day, is a rather wronged character. Everyone thinks she’s a charlatan and misses predictions, but she got several right – only nobody noticed.
In The Prisoner of Azkaban, she says that Harry was born in the middle of winter. He replies that he was born in July (which is midsummer in the northern hemisphere).
But – amazingly – who was born in winter? Tom Riddle, aka Voldemort, was born on December 31st. Since Harry was a Horcrux all along, Trelawney guessed the birth date of the part of Voldemort that inhabited the boy.
4) Dumbledore found the Room of Requirement before Harry did
Even before Harry found the curious room, he heard Dumbledore talking about it. In The Goblet of Fire, fourth book in the saga, Harry is having dinner with the champions of the schools and with the teachers. Dumbledore tells an interesting fact that happened to him: “Even this morning, on my way to the bathroom, I turned the wrong way and found myself in a room of beautiful proportions, full of chamber pots, that I had never seen before. When I went back to investigate it more closely, I found that the room was gone. But I need to stay tuned to find him again. Perhaps it only appears when the person looking for it has a full bladder”. And Harry still has the impression that the headmaster winks at him after telling him this.
The Room of Requirement only really becomes part of the story in the fifth book, The Order of the Phoenix, when Harry and his colleagues need a secret place to train Dumbledore’s Army.
5) Snape’s lessons in the first book predated future events
On Harry’s first day of class in Philosopher’s Stone, Snape decides to pester him by asking difficult questions. The first thing he says is, «Potter, tell me, what would I get if I added powdered asphodel root to a wormwood infusion?» Then he asks, «Potter, where would you look if I asked you to find a bezoar?»
According to the Victorian Flower Language, an encyclopedia of flowers, asphodel is a type of lily (which in English is «lily», the same name as Harry’s mother) and means: «my regrets follow you to the grave». “Losna” means absence and represents sadness. Adding the two things together, we can interpret that Snape was mourning Lily’s death.
And the bezoar? In Half-Blood Prince, Harry finds a potions book with old notes written on the edges (made by Snape himself!). They mention that bezoar is an antidote for poisons. When Ron is later accidentally poisoned, Harry remembers the bezoar and uses it to save Ron’s life. Snape’s speech in the first book somehow references these events 6 years later.
6) The missing closet has appeared several times
In the sixth book, The Half-Blood Prince, Harry learns that Draco Malfoy is using a Vanishing Cabinet in the Room of Requirement to connect Hogwarts to a Vanishing Cabinet elsewhere. But such cabinets had appeared before.
In The Chamber of Secrets, the second book in the series, Harry accidentally ends up in Knockturn Alley. He is in a store, Borgin and Burkes, when the Malfoys enter. Harry seeks hiding in one of these cabinets, which was there. Already in The Order of the Phoenix, Fred and George Weasley lock the Slytherin Montague in a closet – and he says that he could hear things that happened at Hogwarts and also at Borgin and Burkes – it was, therefore, one of the Vanishing Cabinets.
7) Slytherin’s Locket is found by Harry in the fifth book
One of the Horcruxes, Slytherin’s Locket, had been stored in a cave. From there it was retrieved by Regulus Black and his house-elf Monster. Regulus died on the mission, but Kreacher returned to the House of Black with the artifact.
In The Order of the Phoenix, Harry, Ron and Hermione are in the house because it houses the Order of the Phoenix. They clean the place under Molly Weasley’s orders. They eventually find a closet full of trinkets, including «a heavy locket that none of them could open». It was Slytherin’s Locket! Without knowing it, Harry had in front of him, without any difficulty, one of the Horcruxes.
8) The diadem of Ravenclaw also accidentally appears
Like the Medallion, the Diadem also appeared earlier in the book series. In The Half-Blood Prince, Harry hides his potions book in the Room of Requirement under the bust of an ugly wizard. On this wizard’s head, Harry puts on a dusty wig and «a tarnished tiara… to make him more distinguished».
9) The curse of the 13 and the death of Dumbledore
In The Prisoner of Azkaban, Professor Trelawney refuses to sit at the dinner table for Christmas dinner. She warns Dumbledore: «I dare not, Headmaster! If I sit down, there will be 13 of us! Nothing is bad luck anymore! Never forget that when 13 dine together, the first person to rise will be the first to die.”
Ron Weasley was sitting at the table and – most likely – had Scabbers the mouse in his pocket. Afterwards, we found out that the animal was, in fact, the animagus Pedro Pettigrew. They were already therefore 13 having dinner together. And Dumbledore got up first (precisely to invite Trelawney to the table). He is the first of that group of people to die.
There’s more: in The Order of the Phoenix, Sirius is the first to stand up at a table where 13 people are dining. He dies in the same book. And in the last book, The Deathly Hallows, 13 people manage to go to the Burrow after the Battle of the 7 Potters. Lupine is the first to rise, offering to search for Alastor Moody’s body. Afterwards, he is the first to die in the Battle of Hogwarts.
10) The story of Snape and Lily is hinted at as early as the fifth book
When Harry and Dudley are attacked by dementors, in The Order of the Phoenix, the protagonist cannot explain well to Uncle Vernon what the creatures are. “They guard Azkaban Prison,” Aunt Petunia replies promptly, immediately covering her mouth with her hands, as if she had said something terrible.
When Vernon asks how she knows that, the woman replies «I heard that horrible boy telling her that years ago». Harry assumes – and so do we – that “the horrible boy” is her father, James. But, in the flashback that appears in The Deathly Hallows, we learn that the boy is Severus Snape, who was a friend of Lily’s when he was little.
11) Aberforth, the Informant
Voldemort asks Albus Dumbledore for a teaching job, as Harry sees in the headmaster’s memoirs in The Half-Blood Prince. Dumbledore turns down the job and claims he already knows about Death Eaters. The villain is furious and says that Dumbledore is «more omniscient than ever».
“No, no,” he replies. «I’m just friends with the local bartender.» In The Deathly Hallows, we find out who the bartender is: Aberforth, Dumbledore’s brother.
12) Harry and Ron accidentally predict the events of The Goblet of Fire
On a homework assignment for the Divination class, the friends decide to make up their predictions to get it over with. They contrive that Harry will be in danger of being burned, that he will lose a precious possession, that he will be betrayed by someone he thought was his friend, and that he will come back worse from a fight.
Such predictions refer, respectively, to the task against the dragon, to the “abduction” of the friends of each champion in the second task, to the true identity of Professor “Mad-Eye” Moody and to the confrontation against Voldemort.
13) Ron and Hermione’s Patronuses Have a Curious Relationship
In a scene from The Deathly Hallows, Harry observes that Ron and Hermione have fallen asleep holding hands. Hermione’s Patronus is an otter, an animal that often sleeps this way with other otters. And there’s more: Ron’s Patronus is a terrier dog, known for hunting otters.
14) Warlocks’ patrons change because of love
This powerful spell changes according to our emotions. Snape’s changes to a doe (Lilian Potter’s Patronus) after Harry’s mother dies. Tonks’ Patronus, which was originally a hare, changes to a wolf after she falls in love with Lupin.
But the spell also changes with brotherly love. After the death of his brother, Fred, George was never able to conjure a Patronus again.
15) Dumbledore knew since The Goblet of Fire that Voldemort couldn’t kill Harry
In a passage in the fourth book, Harry, after telling that Voldemort had used his blood to rise again, sees a look of triumph in Dumbledore’s eyes. At this point, Dumbledore’s reaction doesn’t seem to make sense to us readers.
But we discover the truth three books later, in The Deathly Hallows, in the conversation between the two in King’s Cross. Harry asks how is it possible that he survived the Killing Curse. Dumbledore asks him to remember what Voldemort had done.
After reflecting, Harry concludes what the Headmaster already knew: the Dark Lord, by using the little wizard’s blood, could no longer kill him.
16) What Harry Hears When He Meets The Dementors Are Not His Memories
Every time our hero encounters these creatures, he hears his parents’ screams before they die. Horrible, isn’t it? But, come to think of it, there was no way he could remember that night, since he was just a baby.
This leads us to believe that, since Harry carried a piece of Voldemort’s soul with him, he was reliving the villain’s worst memory: the moment when he was almost defeated.
17) Dumbledore’s reward given to Neville has to do with the headmaster’s past
At the end of Philosopher’s Stone, Dumbledore awards 10 points to Neville Longbottom because, in the wizard’s words, «it takes a lot of courage to stand up to our enemies, and even more to stand up to our friends». At the end of the saga, we see that this is exactly the same decision he made when facing Grindelwald.
18) Neville really belonged in Gryffindor
Several times during the saga, Neville is concerned that the…