Such as how Helena Bonham Carter made one of the actors go deaf and a mistake the three leads made that ended up in the movie.

While filming the fight scene in the Department of Mysteries, Helena Bonham Carter put her wand in Matthew Lewis' ear, pretending to torture it.

And accidentally perforated his eardrum when he suddenly moved his head.

She felt awful about it, but fortunately, it healed, and Matthew Lewis got his hearing back a few days later.

Bellatrix Lestrange wasn't originally going to be played by Helena Bonham Carter.

At first, they were going to cast Helen McCrory, but because of her pregnancy, she had to be replaced.

However, McCrory made it into the Harry Potter universe later on, by being cast as Narcissa Malfoy in "Harry Potter and the Half-Blood Prince".

Since this film would include wand dueling at an elite level, a dance choreographer was hired to create the movement vocabulary each wizard would use.

Every actor was taught five basic spell-casting moves, and then, they were allowed to adapt the spells slightly to fit their own character.

The Department of Mysteries was a completely computer-generated set.

Because building all the crystal balls in real life would've been too expensive, and they would've taken a lot of time to clean up and reset between takes.

So it may help you appreciate the scene even more to know that everything you see besides the actors wasn't really there during filming.

The Ministry of Magic sets required over 30,000 individually-placed tiles, and the tiles were made out of heavily-painted cardboard instead of real ceramic tiles in order to cut down on costs.

The Black family tree tapestry was hand-painted on a woven tapestry fabric.

An amazing fact about how much J.K. Rowling spent envisioning her world, is when the filmmakers were going to make the tapestry, they called her up to ask if she could help them with any information about Sirius Black's lineage.

Minutes later, Rowling sent them a fax of a document she already had on hand that listed at least 4 generations of the Black family tree, which included nearly 100 names.

Evanna Lynch reportedly beat 15,000 girls for the role of Luna.

The reason why she got the role is because, out of everyone, she was the only girl who the producer thought wasn't just an actor playing a role, but that she was Luna.

In the scene where Harry, Ron, and Hermione are discussing Harry's kiss with Cho, the three break out into laughter.

However, their laughter was them breaking character, because the actors couldn't keep a straight face while talking about kissing.

But the director enjoyed the authenticity of their laughter so much that he used that take in the movie.

The Room of Requirement's lighting was pretty hazardous for the actors and their shoes.

The production designers wanted to make the whole scene glow, so they built some lights into the floor of the set.

The problem was, the lights were so hot that the actors' shoes were getting burned.

So they had to turn the lights down and give the actors some protective shoe covers to avoid damaging their shoes and the floor any further.

Sometimes the length of a book and its corresponding movie don't quite measure up, and there are two examples of this in the Harry Potter franchise.

For example, "the Order of the Phoenix" is the longest book in the series, but oddly enough, it's the second shortest movie.

On the other hand, "the Chamber of Secrets" is one of the shortest books, but it's the longest movie in the series.

Let me know down in the comments if you think one of the Harry Potter movies could've been longer or shorter.

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