Monsters, Inc. hidden details and behind-the-scenes facts

Monsters, Inc. hidden details: Sulley's hair

Pixar's team gave Sulley about 2.3 million individual hairs, and every one had to cast shadows on the others. A new simulation program called Fizt controlled how the fur moved when he ran or turned, which was a major technical leap at the time.

How Boo was recorded

Mary Gibbs, the voice of Boo, was so young that she could not read a script. Most of her lines came from play sessions set up around her, and the crew followed her around the Pixar offices with a microphone to catch her babbling and laughter.

The film had other names

Docter started work in 1996 after pitching the idea in 1994. Early names show how much it changed.

• The project's code name was Hidden City, after a restaurant Docter liked in Point Richmond.
• Sulley was first called Johnson.
• Mike was named after the father of Frank Oz.

Billy Crystal's second chance

Crystal had turned down the role of Buzz Lightyear in Toy Story and later regretted it. When Pixar offered him Mike, he accepted straight away, and he has called it his favourite role.

Crystal's history with Pixar makes the casting a neat piece of luck. Having missed one of the studio's most famous roles, he ended up with another that audiences love just as much, and his fast talking pairs well with Goodman's slower, warmer delivery. Their partnership as Mike and Sulley is the centre of the film, and the easy back-and-forth between the two actors is the main reason the story still works for adults as well as children watching it years later.

A scene changed after September 11

Harryhausen's, the sushi restaurant named after effects pioneer Ray Harryhausen, was originally going to be blown up when the Child Detection Agency arrives. After the September 11 attacks, the explosion was replaced with a containment dome dropping over the building.

Randy Newman's song If I Didn't Have You won the Oscar for Best Original Song, after many earlier nominations. The film set a record opening and passed $100 million within weeks.

The fur problem shaped the whole look of the film. Making each hair shadow its neighbours meant Sulley could look soft and warm, which was essential for a monster children had to love. That realism sits alongside a deliberately cartoonish Mike, one big eye and no fur at all, and the contrast between the two is part of why the pair read so clearly on screen.

Boo's recording sessions were just as unusual. Because Mary Gibbs was too young to follow directions, the animators built Boo's performance around what she actually did, rather than asking her to match a script. Her real laughter and chatter are a big reason the character feels like a real toddler rather than a written one.

Docter's long development period also explains the film's polish. He spent years reworking the story, the characters' names and the world, and the final version keeps only the strongest ideas from those early drafts.

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