It must be tough to direct your first live-action film with Steven Spielberg and Michael Bay looking over your shoulder. But for Travis Knight, director of Transformers spin-off Bumblebee, those two singular filmmakers weren't just the movie's producers, they provided the touchstones that inspired the film.

"ET was my spirit animal in this movie", explained Knight as I sat down with him in London to discuss Bumblebee. "I saw it when I was around 8 years old with my mom in a darkened theater and I was a big, blubbery mess at the end of it ... On some levels Steven's films from that era are responsible for me becoming a filmmaker."

And it shows: Not only is Bumblebee set in the 1980s, but the spirit of '80s movies like ET and Short Circuit shine through in the adorable adventures of a girl and her robot buddy.

Spielberg was a producer on Bumblebee, as was Michael Bay -- the man who resurrected Transformers by directing all five previous movies in the series.

"From a director's perspective he was a dream producer," Knight says of Bay. "We sat down early on and it was great for me, director to director, to pick his brain, to get a sense of his philosophy on the Transformers. He was really respectful and recognized this was someone else's movie, my take on these characters, and the best thing that he could do was to support me and protect me. He let me do my thing, and I'm really appreciative of it."

Bay gave Knight one memorable piece of advice for working on a mega-budget franchise movie surrounded by people from the studio, the toy company and elsewhere all pulling a director in different directions.

"He said the one thing you have to do is protect the movie," Knight remembers. "That was advice Jerry Bruckheimer gave him, and he passed it on to me -- remember the movie you intended to make and protect it." 

Knight's previous filmmaking experience was as an animator, directing the stunning stop-motion film Kubo and the Two Strings.

"Stop motion is probably the subset of animation that's closest to live-action," he says, "in the sense you're physically shooting these things with real lights and real cameras, and there's props and sets and costumes and hair."

But there were still plenty of new things to learn on this, his first live-action film.

"A lot of times I was flying by the seat of my pants," he says, laughing.

Knight brought what he called "an animator's discipline and planning" to the film, mapping out each sequence in detail.

"I do believe in the adage that the trimmer the vessel, the more it can carry," he says. "Animation is very organized and disciplined. You can't shoot coverage, you can't play around. But in live-action, you can play around, and sometimes you'll create little magical moments." 

He particularly enjoyed John Cena's ability to improvise in the role of a burly secret agent pursuing Bumblebee.

"John's like a one-man ad-lib factory. We would do the scenes, and then we get to the end of the scene, I'm like, 'All right, John, now let's play a little bit,' and he would always do something really unexpected. He's just a very, very clever, funny man."

A major criticism of Bay's past Transformers movies is the fast-paced computer-generated action, an assault on the senses that's often hard to follow. While it has plenty of action, Bumblebee tones down the CG carnage. But Knight insists this shouldn't be seen as a criticism of Bay's style.

"It wasn't in any way addressing any feedback from the fans," he says. "It was just a story I wanted to tell. That last one [Transformers: The Last Knight] is one of the biggest movies I've ever seen -- and I couldn't go bigger than that. So let's go the other way, let's focus in on a small corner of this canvas and really get to know one of these characters. Let's balance the emotions with the explosions ... The core relationship mattered to me more than anything else. And if that didn't work, none of the other stuff matters. It's just bombast. It's just eye candy."

Mixing the spectacular, visual effects-driven action with a character-led story was "a high-wire act", but Knight credits writer Christina Hodson for striking the right balance.

"She's gained something of a reputation in Hollywood as this kinda badass chick writer with these cool, action movies," he says, "When you talk to her, the films that she always references are cool action movies like T2 ... But when I sat down and talked to her about the film and my vision of it, I realized very quickly she has a big soft gooey heart just like I do."

Knight's next big project is 2019's Missing Link, a new stop-motion adventure from his animation studio Laika. As for where the Transformers movies go next, Knight is sanguine.

"It's hard to say. I think at this point, candidly, they're probably just waiting to see how people react to [Bumblebee]. If people vote with their wallets for these kinds of Transformer movies, then they'll get these kinds of Transformer movies."

Bumblebee opens in Australia on Dec. 20, in the US on Dec. 21 and in the UK on Dec. 24.

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