A premiere date has not yet been set for Stranger Things season 2

Credit: Ben Trivett

While the Stranger Things Demogorgon remains something of a mystery going into season 2, one thing’s been cleared up: The identity behind the monster.

As it turns out, the Demogorgon isn’t portrayed by CGI – he’s played by a real man in a physical costume named Mark Steger.

“He was amazing!” star Millie Bobby Brown, 12, tells PEOPLE exclusively of the actor. “He was so great. He was this tall guy – I mean, his body movement is amazing.”

And considering the “massive” costume, Steger’s movement was impressively fluid, according to Brown and her fellow Stranger Things costars Gaten Matarazzo, Caleb McLaughlin and Noah Schnapp.

“It takes him about … How long? I thought it’d be like, five hours [to put the costume on],” says Brown.

“He has these remote control hands,” adds Schnapp.

“It’s like he’s pop-locking a little bit!” says McLaughlin with a laugh.

And while Schnapp did admit it was “scary” being on set with the Demogorgon, Brown had a more light-hearted behind-the-scenes story to tell.

“When I was doing the scene where I touched him and then I ran away … he couldn’t feel me, every time I touched him,” she explains. “So then, I’d touch him and he wouldn’t turn back and the Duffer brothers were screaming: ‘Alright Mark, Go!’ And he’s just sitting there, and he can’t hear us. So I just slapped his back and he goes: Rawr!

“And then I was like: ‘Ew, we need to wash this,’ ” quipped Brown of her Demogorgon-slime covered hand.

A premiere date has not yet been set for Stranger Things season 2.