In today’s edition of “things that totally should have been in the movies, Malfoy puts a curse on Neville that locks his legs together, and he has to hop all the way to Gryffindor tower. But rather than being used as an excuse to laugh at him, it’s a chance for Harry, Ron, and Hermione to encourage him to stand up for himself – which he later does, when Malfoy attempts to bully him again at the Quidditch match. This early on in the series, there are very few signs of the hero Neville will eventually grow to be, but this is one of them. I think it’s especially important that not only did he stand up to Malfoy, he did it after being build up and encouraged by the same peers who will eventually include him in Dumbledore’s Army and help him learn to defend himself from much more serious dangers.
In Defense Against the Dark Arts, Quirrell is teaching them how to treat werewolf bites. This seems like an early inconsistency to me, because werewolf bites can’t be treated. Even injuries like Bill Weasley’s, which don’t turn him into a werewolf, leave scars that no magic can get rid of. Werewolves in general are portrayed differently in the first two books as compared to the rest of the series. Malfoy is afraid of werewolves in the forest, Hagrid says they’re too slow to be the creature killing the unicorns, and in Chamber of Secrets, Tom Riddle says a young Hagrid tried to raise werewolf cubs under his bed. Quite different from the werewolves of later books, who are fully human except on the night of the full moon. On Pottermore, Rowling has given a very odd explanation, but I have to assume it’s just something she hadn’t thought through yet when writing the early books. In a series this long and complex, there had to be something that’s not consistent all the way through.
However, other details that don’t become important until many books later are surprisingly well-foreshadowed. For example, Rowling tells us that “[Harry] sometimes had the horrible feeling that Snape could read minds”. Well, as Snape will later explain, “the mind is not a book to be opened at will and examined at leisure”, but Snape is in fact a skilled legilimens. To someone like Harry, who has no training in occlumency and no skill for it once he starts learning, it must really seem like Snape is reading his mind. Every thought or emotion is right out there to be seen by anyone capable of legilimency.
The whole dragon sequence is very different from the movie version. Instead of being caught by McGonagall and then Dumbledore sending the dragon away, Harry and Hermione smuggle the dragon out via Ron’s brother Charlie. It’s only on their way back to their dorm that they’re caught, and McGonagall seems to think they tricked Malfoy into thinking they had a dragon just to get him in trouble. This was probably changed to make it shorter for the movie, but the book version works better, and explains why they’re only in trouble with McGonagall. Keeping a dragon is a serious crime, and if the dragon was definitely there, it’s hard to imagine that Malfoy wouldn’t tell his father or that his father wouldn’t try to do something with that information. Send Hagrid to Azkaban. Get Dumbledore fired. Something.
In the forest, when Hagrid, Harry, and Hermione run into a centaur named Ronan, he is not surprised to hear about the injured unicorn and says that the innocent are “always the first victims”. Later, when Voldemort returns, his first victims are an absent-minded Ministry employee, an elderly muggle man, and Cedric Diggory. All of these people are innocent, both in the sense that they’re good people who don’t deserve to die, and in the sense that they’re ordinary people in the wrong place at the wrong time, rather than combatants in the war. In fact, Frank Bryce is literally innocent of a murder most people blame him for, which was actually committed by Voldemort. Voldemort’s first victims when he rose to power as a young man were also innocent: a Hogwarts classmate, his muggle father and grandparents, a woman who trusted him with her secrets, and the people he framed for their deaths.
But a far more important bit of foreshadowing comes when Bane finds out Firenze has saved Harry’s life. “We are sworn not to set ourselves against the heavens,” he says. “Have we not seen what is to come in the movements of the planets?” If what they had seen was Harry’s death in the forest at Voldemort’s hands, they’re six years early.