Though the werewolf we see on-screen was created by computer, initially the creature designers for Harry Potter and the Prisoner of Azkaban had some ambitious plans to achieve the effect practically...

A werewolf in the forest from the Prisoner of Azkaban
Harry Potter and the Prisoner of Azkaban

Extracted from Harry Potter: The Creature Vault by Jody Revenson
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While an Animagus chooses to turn into their animal form, like Professor McGonagall in Harry Potter and the Philosopher’s Stone and Peter Pettigrew in Harry Potter and the Prisoner of Azkaban, a werewolf has no choice but to change, a transformation that occurs at the rising of the full moon.

Werewolf example 1.

Remus Lupin

It is established in Harry Potter and the Prisoner of Azkaban that Remus Lupin, while a child, was bitten by the werewolf Fenrir Greyback. As an adult, he is able to take Wolfsbane Potion to control his condition, but he still struggles with the shame and weight of his secret, which the filmmakers brought out through costume and makeup.

Lupin as a werewolf
Harry Potter and the Prisoner of Azkaban

With more than one hundred werewolf transformations filmed throughout the history of cinema prior to Remus Lupin’s, the visual development artists for Harry Potter and the Prisoner of Azkaban were eager to give this iconic character a fresh approach. Inspiration came from depicting Lupin’s condition as an illness. To that end, his pallid face and scarred body mark his struggle against the affliction, and his grey, shabby clothing add to the idea that he has faced much hardship and paucity.

Lupin’s werewolf form isn’t meant to be as scary as conventional movie werewolves; there is a gravity and sadness about him. His makeup design is lupine but retains some of his humanity. Lupin’s werewolf form is thin and disfigured, almost emaciated, with long limbs and a hunched back. One significant change from most movie werewolves is that Lupin is relatively hairless.

A sketch of a werewolf in the forest from The Prisoner of Azkaban
Harry Potter and the Prisoner of Azkaban

The creature designers began with the hope that they would be able to achieve the werewolf transformation practically, with prosthetics and animatronics. They decided to sculpt the werewolf they wanted without worrying how they would install someone to control the sculpt. The result was an extraordinary creature that was extremely tall (seven feet) and extremely thin, and would require a performer with a unique skill set who could fit inside. A kick boxer and a dancer were cast and trained for several months wearing three-foot-tall reverse stilts to give them the necessary height and stride. When they were brought to the actual set featuring the Whomping Willow, it became apparent that the performers could not achieve the same effect they had in rehearsal. The costume was tight and restrictive, not allowing the creature to be as athletic as desired. Additionally, as the scene’s set was an undulating hillside strewn with rocks and tall grasses, the performers labored for balance and could not move as quickly across the terrain. Because of these reasons, it was determined that the final werewolf seen on-screen would need to be created by computer.

Up until Lupin completes his transformation, practical and makeup effects were combined to span the transition from human to werewolf. Actor David Thewlis (Remus Lupin) was fitted with several stages of prosthetics that changed his eyes, teeth, and hands. Other effects included a cable-controlled piece under the back of his coat that expanded to rip apart the material, and bladders on his neck that inflated. Visual tricks included a cutaway shot of the actor’s feet elongating and stepping out of his shoes.

Harry Potter: The Creature Vault book cover

Extracted from
'Harry Potter: The Creature Vault'