While not the most pleasant of creatures, a troll served as the focal point of one very key scene. After all, it was the very scene which cemented the friendship of Harry, Ron and Hermione.

The troll in the girls bathroon with Harry's wand up his nose
Harry Potter and the Philosopher's Stone

Extracted from Harry Potter: The Creature Vault

Trolls are described as extremely large creatures, roughly twelve feet in height. They are very dangerous and very stupid. A troll first appears in the films when, during the Halloween feast in Harry Potter and the Philosopher’s Stone, Professor Quirrell races into the Great Hall shrieking that there is a troll in the dungeon. When Harry Potter and Ron Weasley find Hermione Granger—and the troll—in the girls’ bathroom, they manage to defeat it when Ron is finally able to correctly use the Wingardium Leviosa spell.

The troll sequence in Harry Potter and the Philosopher’s Stone uses a blend of several types of visual effects techniques. First, the creature shop designed a troll and constructed a maquette that included his vacant expression, three-toed limbs, and the large spiky warts on his legs. Next, a full-grown painted and costumed troll model was fabricated, as it was needed when the troll is knocked out on the girls’ bathroom floor. Additionally, the troll’s hand and his lower half, including his legs, were produced at full size for Emma Watson (Hermione Granger) to act against.

Another actor performing in a troll costume was filmed by a traditional camera for digital reference, as Philosopher’s Stone was shot years before motion capture technology became prevalent. The practical sight gags were filmed: the bathroom doors exploding from a strike of the troll’s club, the sink being destroyed above Hermione, and a hydraulic rig raised Daniel Radcliffe (Harry Potter) to ‘drop’ on top of the troll’s shoulders and swing about. All these live-action shots were placed in the proper timeline for the scene and then composited with digital footage to create one continuous scene.

Hermione face to face with the Troll in the girls bathroom
Harry Potter and the Philosopher's Stone

Trolls were proposed to appear in another of the Harry Potter films, Harry Potter and the Half-Blood Prince. The filmmakers had intended to use them in a ‘moving’ tapestry, in the same way the photographs and paintings were animated. Two dancers wearing troll suits outfitted with pink tutus and ‘toe’ shoes were filmed for a tableaux portraying Barnabus the Barmy teaching trolls to dance ballet. In fact, the performers were filmed dancing in front of a blue screen a total of four times so that an octet of trolls would perform the choreography together. Their dance, which landed on the cutting room floor, was named the pas de trolls.

Harry Potter: The Creature Vault book cover

Extracted from
'Harry Potter: The Creature Vault'