1) Peeves

Peeves is a poltergeist in the Harry Potter books who gets up to a lot of mischief. Ironically enough he is a vital character to making these books the children’s series they are meant to be. For the first film Sorcerer’s/ Philosopher’s Stone, Rik Mayall was set to play Peeves. Unfortunately, his scenes were not ready in time and had to be cut from the film. Subsequently, no other producers or directors chose to reincorporate Peeves into the films. This makes me very sad, mostly because of Peeves’ relationship with the Weasley twins, Fred and George, is highly entertaining within the books.

"Give her hell from us Peeves!" -Fred and George Weasley (Harry Potter and the Order of the Phoenix by J.K. Rowling)

2) Ron Weasley’s Moments

This has been a concern of hardcore Potter fans for years. Most of Ron’s greatest moments were changed or his awesome lines were given to Hermione in the films. Now, I know what people are going to say, I want proof. Here are a few examples:

In the book for Sorcerer’s/ Philosopher’s Stone, when Harry, Ron, and Hermione go down the trapdoor attempting to apprehend the thief of the Stone, who they believe to be Professor Snape, they must pass through obstacles. One obstacle is the Devil’s Snare, created by Professor Sprout. When stuck in these vines, Hermione remembers that Devil’s Snare dislikes fire, but then panics and shouts about needing matches for light, while being strangled to death. It is Ron who shrieks at her that she’s a witch with a wand and that she knows spells. On the other hand, in the film, it’s Ron who panics and Hermione who rescues him. This small change puts Ron into a bad light almost making him seem stupid to the audience.

Another instance of mistaken identity happens in the third book, The Prisoner of Azkaban when Hermione and Ron believe Sirius Black is after Harry. Ron bravely stands on his injured leg and shouts at who he believes to be a wanted criminal and murderer that if the man wants Harry, he has to go through his friends first. In the film though, Hermione steps forward and steals this moment and line. It’s almost like they wanted Hermione to seem braver than Ron, which is great for a brave girl to be shown, but wrong to demean Ron.

Again in Prisoner of Azkaban, in the book, Professor Snape asks a question of his students and Hermione immediately answers. Snape calls her a know-it-all, which is true, but as a good friend Ron steps up and defends her saying, “You asked us a question and she knows the answer! Why ask if you don’t want to be told?” by which he loses tons of house points for Gryffindor. In the movies, though, after Snape insults Hermione, Ron gives Hermione a strange look and says, “He’s right, you know.”

All these changes make Ron a coward and a jerk when in the reality of the books, Ron is brave and loyal.

3) The Explanation of The Deathly Hallows

In the films, Deathly Hallows Part 1 and Deathly Hallows Part 2, the Deathly Hallows are explained, but not in great detail. We are shown bits and pieces of the whole story. To understand how significant these items are, we really need to read the relevant passages in the book, which give so much more detail and information than the films chose to.

4) Voldemort’s Actual Death

When Voldemort fires the Killing Curse from the Elder Wand and it hits Harry's Disarming Charm, the Elder Wand flies out of Voldemort's hand into Harry's hand and the Killing Curse is directed towards Voldemort. Harry has been proven right, as in this moment, the Elder Wand refuses to kill its true master, Harry. Voldemort no longer had the protection of his Horcruxes, but since his soul is broken because of creating the Horcruxes themselves, he does not actually die. He is gone, completely vanquished of power and life, but stuck in the limbo stage between life and death for all eternity.

“… Voldemort fell backward, arms splayed, the slit pupils or the scarlet eyes rolling upward. Tom Riddle hit the floor with a mundane finality, his body feeble and shrunken, the white hands empty, the snakelike face vacant and unknowing. Voldemort was dead, killed by his own rebounding curse, and Harry stood with two wands in his hands, staring down at his enemy’s shell.” (Harry Potter and the Deathly Hallows by J.K. Rowling)

In the movie, though, Voldemort turned into papery stuff and floated off into the wind. This was stupid. We needed to see him die with a body and we need to know that he was not all-powerful and immortal. We needed to see that he was still just a person, but a person who had committed crimes worse than anything else imaginable and he could still die a human death!

5) Harry’s Epic Speech At The Final Battle

That brings me to my next point, they took Harry’s explanation speech in this final battle away. He says in the film to Voldemort, “Let’s finish this, the way we started it. Together.” In the book we get this amazing scene:

Voldemort’s hand was trembling on the Elder Wand, and Harry gripped Draco’s very tightly. The moment, he knew, was seconds away.
“That wand still isn’t working properly for you because you murdered the wrong person. Severus Snape was never the true master of the Elder Wand. He never defeated Dumbledore.”
“He killed --- ”
“Aren’t you listening? Snape never beat Dumbledore! Dumbledore’s death was planned between them! Dumbledore instended to die, undefeated, the wand’s last true master! If all had gone as planned, the wand’s power would have died with him, because it had never been won from him!”
“But then, Potter, Dumbledore as good as gave me the wand!” Voldemort’s voice shook with malicious pleasure. “I stole the wand from its last master’s tomb! I removed it against the last master’s wishes! Its power is mine!”
“You still don’t get it, Riddle, do you? Possessing the wand isn’t enough! Holding it, using it, doesn’t make it really yours. Didn’t you listen to Ollivander? The wand chooses the wizard . . . The Elder Wand recognized a new master before Dumbledore died, someone who never even laid a hand on it. The new master removed the wand from Dumbledore against his will, never realizing exactly what he had done, or that the world’s most dangerous wand had given him its allegiance . . .”
Voldemort’s chest rose and fell rapidly, and Harry could feel the curse coming, feel it building inside the wand pointed at his face.
“The true master of the Elder Wand was Draco Malfoy.”
Blank shock showed in Voldemort’s face for a moment, but then it was gone.
“But what does it matter?” he said softly. “Even if you are right, Potter, it makes no difference to you and me. You no longer have the phoenix wand: We duel on skill alone . . . and after I have killed you, I can attend to Draco Malfoy . . .”
“But you’re too late,” said Harry. “You’ve missed your chance. I got there first. I overpowered Draco weeks ago. I took his wand from him.”
Harry twitched the hawthorn wand, and he felt the eyes of everyone in the Hall upon it.
“So it all comes down to this, doesn’t it?” whispered Harry. “Does the wand in your hand know its last master was Disarmed? Because if it does . . . I am the true master of the Elder Wand.”
(Harry Potter and the Deathly Hallows by J.K. Rowling)