The Harry Potter movie adaptations mostly kept to the storylines directly connected to Harry’s time at Hogwarts and his connection to Voldemort. To make sure that the story made sense all the way through, many things had to be cut out of the film. However, to try and fill in the blanks and backstories, the movies had to incorporate some elements from the books. In doing so, the movie audience got a taste of the bigger picture. The film never expanded on the conflicts surrounding Snape, Sirius, and Remus, but they gave enough to understand why there was tension between them. Snape’s perspective is used to show his redemption, but not to show how he was a problem.
Harry’s lessons with Dumbledore in Harry Potter and the Half-Blood Prince to watch Voldemort’s memories are cut to the most critical moments, such as a young Tom Riddle with treasures and his questions about Horcruxes. But, other moments of young Tom Riddle and understanding his backstory are ignored in favor of turning the film’s tone into something more akin to a romantic comedy between Harry’s wish to date Ginny and the love triangle between Hermione, Ron, and Lavender.
Voldemort’s backstory never gets the pacing or screen time it deserves to flesh out the character to the fullest extent. Given how Voldemort is known as the villain, the movies do not spend as much time highlighting his growth to power or motivations behind a wizarding world takeover.
While the series makes it clear that he was a terrifying enough villain to the point where everyone was too frightened to say his name, the movies do not devote as much time to understanding his childhood, young adulthood, and how the he made as an adult were foreshadowed by his wish to steal significant treasures as a child.
Hermione and Ron’s Romance
Even though Hermione and Ron’s romance does not get that much time in the novels either, at least more moments could have hinted toward it. Since the books and movies mostly take place from Harry’s perspective, it was rare that Hermione and Ron had scenes without Harry being present. Due to that, Ron and Hermione were rarely seen alone together.
The movies could have expanded on giving them moments together, at least so that Hermione’s friendship with Harry did not come across as a more obvious potential pairing.
Harry and Ginny’s Relationship
Harry and Ginny’s romance in the books is not exactly a thrilling tale, either. However, the movies make it far more difficult to follow. Considering Harry barely spends time with Ginny in the films, he goes from having almost nothing to do with her to growing a crush on his best friend’s younger sister. In the novels, Harry and Ginny, while not given plenty of time alone together either, at least are given a slightly larger friendship foundation to go off of, as well as more time in the books to be a romantic couple.
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Dobby’s plot is best utilized in Harry Potter and the Chamber of Secrets. He is desperate to help and save Harry, going about it in all the wrong ways, and it is eventually discovered that his Masters are the Malfoys. Rather than allow Dobby to remain in an abusive environment, Harry tricks Lucius into freeing Dobby. But, in the movies, that is the last anyone sees of Dobby until Harry Potter and the Deathly Hallows: Part 1.
In the novels, Dobby returns in a supporting role. He gets a job at Hogwarts and helps Harry find a solution for the second task instead of Neville. While Dobby may not have been able to appear in every film, his role and how the books bring in Winky to portray a different side of the House Elf experience could have helped the movies expand on the wizarding world.
Dumbledore’s backstory with Abeforth, Ariana, and Grindelwald is briefly touched on in the movies. It is explained just enough to know that Dumbledore’s family backstory was far darker than Harry realized. However, it is never expanded on as much as it could have been, and fleshing it out more could have added exciting layers to Dumbledore’s movie counterpart.
Fred and George’s Joke Shop
In the novels, Fred and George’s plans to open a joke shop are a big supporting plot. As the twins prepare to complete their education, they want to take their love of pranks to a professional level, opening a shop to continue encouraging people to find fun and enjoyment in life. Fred and George’s interest in a joke shop is never mentioned as a film storyline.
While slightly teased when they make their grand exit from Hogwarts, the appearance of Weasley’s Wizard Wheezes comes across as more random than years’ worth of preparation.
The Marauders, Lily, and Snape
In the movies, it is simplified to that James bullied Snape, Snape loved Lily, and Lily chose James and the Marauders, resulting in Snape’s endless bitterness. In the books, it is far more complicated than that. Snape is never the innocent victim he portrays himself as, discovering and creating many dark magic spells.
James, Sirius, Remus, and Peter bully Snape, but Snape also has a nasty habit of getting into their business to discover if Remus is a werewolf. Snape also used a slur against Lily, while the Marauders had eventually matured. Lily had attempted to keep a friendship with Snape, but could not hold on when she finally saw in him whatever everyone else had known for years.
Bill and Fleur
Bill and Fleur’s relationship is explained and shown in multiple installments in the books. While it is never a main plot, there is far more detail showing Molly and Ginny’s initial dislike of Fleur and how she continued to prove herself as someone who loved Bill. Even though Molly and Ginny are still not thrilled by the time the wedding comes around, there is far more understanding about everyone’s relationships.
In the movie, Bill and Fleur’s wedding comes out of nowhere. There is no build-up to their relationship, and without reading the book, no way to understand how Fleur and Bill ended up at the altar. Expanding on this storyline in the movies would have allowed for their wedding to come across as less random and confusing.
Percy Weasley’s Estrangement from the Family
Percy’s estrangement from the family is a minor plot in the movies. He is not in Harry Potter and the Order of the Phoenix until he appears at Minister Fudge’s side, and the refusal to dive into this storyline suggests no real problems. Except, that is very much not the case. Percy’s issues with the family and how the Ministry brainwashes him become very important in the novels, especially as Percy’s moment of redemption comes when he joins his family during the Battle of Hogwarts.
The movies barely considered this a plot to the point where it is never directly shown as relevant, and the way the Ministry’s refusal to acknowledge Voldemort’s return affected families, especially the prominent family, would have been a viable storyline.
Remus and Tonks
Another relationship that falls through the cracks, the Harry Potter movies never address Remus and Tonks’s growing romance until they are already married. Without the angst and mystery that comes from seeing their relationship build in the books, their film romance comes out of nowhere, and it comes across as more that they just wanted to pair them up for stakes. Later discovering that they are going to have a baby lacks the same emotional significance that occurs in the books when Remus briefly gives in to his fears and asks to join Harry, Ron, and Hermione’s journey.