Pixar classic Monsters, Inc. has turned 15 (in the US, at least - its UK release was February 2002) and director Pete Docter has reflected upon its legacy in a brand new interview.

The film - Pixar's fourth feature following Toy Story, A Bug's Life and Toy Story 2 - follows Mike Wazowski (Billy Crystal) and Sully (John Goodman) to monsters based in Monstropolis, a city that is powered by children's screams.

Speaking to EW, Docter - who was the first director to oversee a new Pixar film following John Lasseter's first three - reminisced on the film's challenging development.

"So then when it came out, that was great and I felt like, okay, I didn’t screw up."

It's also emerged that Monsters, Inc. was very close to being extremely different.

"Mike was not in the first draft," Docter revealed. "Our first movie was about Sulley and this kid, and then in subsequent story note sessions, we thought it would be nice for Sulley to have a little bit more of a backstory and a world that gets upset. So we came up with [this] random background character that Ricky Nierva had drawn."

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Prequel Monsters University followed in 2013 showing characters Mike and Sully at Scare School, but would Docter be upf or returning for MOnsters Inc 3?

He's not counting it out: "You never say never - who knows what will happen?

‘We purposely went with a prequel for Monsters University because we didn’t want to answer some of the questions about what happens to Boo, and how does she grow up, and things like that. It would have to be really compelling, which is hopefully the benchmark for all of our sequels, anyway."