Sometimes book-to-movie adaptations can be virtually flawless. In fact, in certain cases the movie can end up being better than the book.

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However, every now and again there'll be a book-to-movie character adaptation that's so bad it kinda ruins the whole thing.
Perhaps it's Ginny from Harry Potter, who was pretty badass in the books but not so much in the movies.

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Or maybe it was Emma in One Day, whose accent was more than a little distracting.

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Or perhaps it was a casting decision that failed to match the vision of the characters you had in your head.

Warner Bros