Harry Potter: Book vs Movie

In "The Sorcerer's Stone" (1997) book, Harry Potter is described as having his mother's bright green eyes. Actor Daniel Radcliffe has blue eyes and was found to be allergic to colored contact lenses. As a result, Harry's eye color differs from the books to the films.

In the "Chamber of Secrets" (1998), Draco Malfoy refers to Hermione as a mudblood, a wizard born to Muggle parents. In the 2002 film version, Hermione is familiar with the insult, whereas in the book, she needs to have it explained.

First-year students at Hogwarts aren't technically allowed to own brooms. So in the "Sorcerer's Stone" (1997) book, when Professor McGonagall arranges for Harry to receive a Nimbus 2000 for use on the quidditch field, she sends a note telling him not to open the package in front of everyone.

In the 2001 film, however, Harry is given no such instruction and opens the gift in the Great Hall.

As is known by Dumbledore and discovered by Hermione, journalist Rita Skeeter is an unregistered Animagus, able to transform into a blue beetle and thereby eavesdrop on conversations undetected.

In the "Harry Potter" films, none of Rita Skeeter's backstory is ever revealed, nor is she shown to be an Animagus.

In 1999's "Prisoner of Azkaban" book, Uncle Vernon refuses to sign Harry's permission slip, meaning that he is unable to go to Hogsmeade with the other students. After Sirius Black is revealed to be Harry's proper guardian, he signs the permission slip.

This detail is left out of the film, leaving viewers to wonder how Harry got permission to go.