6. ‘Toon Army

For the look of Carl and co, Docter decided to stylize, rather than trying to make the characters appear real.

"Characters are always hard,” he admits. “I did a bunch of animation on Toy Story, and, in my opinion, the humans were the least successful part. It's the whole thing of the ‘uncanny valley’ (where the characters’ creators stretch for realism, but they just seem almost real - and so weird and a bit creepy).

"So we've tried to keep them stylized, but still get the essence of who they are, which, of course, is what animation is all about.”

Carl is designed as a square character, which reflects his personality. “He's stuck in his ways,” says Docter. "He's had the same breakfast for the last 50 years, he has the same schedule. And so everything that happens disrupts him.”

Despite the cartoony nature of the film, the technical challenges were still, well, challenging.

“The hardest thing was the look," says Docter. "We have trained our Technical Directors to do almost everything. And we said, ‘Alright, on this film, we want you to do all of that, but we want you to do it wrong!’

“We have a character who, instead of six heads tall, he’s three heads tall. He’s got these short, little, stumpy arms... The way cloth would behave, ignore the way it works in real life. Here’s how I want it to look in this film...’

"So we had to subvert everything we knew. It was really hard to achieve, both artistically and technically. Hopefully, it’s not obvious, it’s kind of invisible...”

The characters were coming along. But they needed to be brought to life…

Next: Getting The Voices