Eddie Redmayne battled Maisie Williams with a plastic spear to prep for Early Man

Some actors take their research very seriously.

Daniel Day-Lewis, for example, recreated a couture Balenciaga gown to prepare for Phantom Thread. And when it came time for Eddie Redmayne to portray an animated caveman named Dug in Early Man, he was ready to go full Neanderthal in his preparation alongside costar Maisie Williams.

“Maisie Williams and I went down to Bristol, where Aardman [Animations] are, and got dressed up as cave people in massive cave suits and stabbed each other with plastic spears,” he tells EW.

Redmayne likens Aardman’s stop-motion studio to Willy Wonka’s chocolate factory. “It’s the most extraordinary place,” he says. “[They have] all these stunning sets that are colorful and vibrant and lifelike, and yet they’re miniscule. And then they have a whole area that’s just the characters’ mouths — like hundreds of thousands of different versions of Dug’s mouth with different expressions. … But they also have this zone which is where the animators go up and get dressed up in huge caveman outfits and film themselves playing the characters, so they can then model from that.”

Though his playful session with Williams was the only time Redmayne got deep into what he’d describe as “research” into early man, he also had to tackle his very first voice acting role. “It’s weirdly much more physical than I expected,” he says. “Because you’re trying to channel all of the character’s traits into just your voice, which, for me, meant that I sort of put my back out and do weird things with my arms.”

Redmayne’s natural speaking voice has been replaced by a slightly different dialect and pitch. Finding the right sound for Dug was a process of trial and error that largely stemmed from studying the look and feel of the character. “He has a massive mouth, which conveniently I have, and huge eyes and kind of eternal optimism,” Redmayne explains. “So I fooled around for about an hour and a half with lots of different voices, but with really wide eyes and a wide mouth, and somehow ended up with that one. I wish I could say there was any more delicate a process, but it was just like throwing mud at a wall and then trying to sculpt it.”

For Redmayne, appearing in an Aardman production was an opportunity to be a part of a British cultural institution. “Aardman and Nick Park are such an institution in Britain. You grew up watching Wallis and Gromit and Chicken Run and those films, and the Creature Comforts,” he says. “When I got the call, it was one of those slightly dreamlike moments.”

Still, Redmayne’s Early Man role was not without its challenges. Namely, correctly pronouncing the name of Dug’s pet pig, Hognob, a riff on the popular British cookies biscuits Hobnobs. “Because Hobnobs are one of my favorite biscuits, it took me a long while to be able to say Hognob,” Redmayne admits. “I kept naming our Hognob after said chocolate biscuit.”

Early Man hits theaters Feb. 16.