Remaking a movie is a tall order, and transitioning a story from another medium to film is even tougher. So it’s no surprise that details frequently get changed to accomodate a new era of filmmaker or the different “beats” associated with a feature-length movie.
It becomes a problem, however, when one of the things cut to accomodate an extra action scene turns out to be vitally important to the plot, leaving the movie with a scene or detail that only makes sense if you’re familiar with the original.
7. In Harry Potter and the Deathly Hallows Part 2, Snape’s Patronus Means Nothing
Working on the film adaptation of Harry Potter before the books were finished created the pretty obvious problem of not knowing exactly what to include — a problem exacerbated by the fact that JK Rowling was clearly making it all up as she went along. Nowhere is the issue more apparent than at the climax of The Deathly Hallows Part 2, where everyone in the audience who read the books was crying uncontrollably and everyone who hadn’t was poking them and asking, in a suitably polite movie-theatre whisper, what the hell was going on.
The scene shows Snape revealing, for the first time, his Patronus: a doe. The book had at this point casually explained that love for someone else can alter a person’s patronus — Tonks’ patronus is a wolf, symbolizing her love for Remus Lupin, who is a werewolf. When we see Snape’s Patronus as a doe, we suddenly realize that he was in love with Lily Potter, Harry’s mother — which explains virtually everything he’s done up to this point. Kinda. If you squint.
But in the movie, we never see Tonks’ patronus, or learn in any other way that a Patronus reflects love at all, making this scene entirely incomprehensible unless you knew what it meant anyway.