"It was almost like a really slow exorcism to completely let go of him," Skarsgard tells PEOPLE

Bill Skarsgard was born in 1990, the same year Stephen King’s novel It was adapted into a TV series starring Tim Curry — but even as a little kid, he remembers his older brothers teasing him with ghost stories about Pennywise the Dancing Clown.

“I never had a clown phobia or anything growing up, but the TV movie came out the same year I was born, and I remember later hearing my older brothers and cousins talking about the scariest movie ever and the clown called It,” he tells PEOPLE.

Now, Skarsgard, 27, one of acclaimed actor Stellan Skarsgard’s seven children, has inherited the role that, as he says, “turned clowning from something jolly to something menacing” for a generation of kids — and adults.

The baby-faced heartthrob, one of three actors in the handsome, Swedish Skarsgard clan, is unrecognizable behind the clown makeup and prosthetics — but playing dress-up has always been his passion. “I spent a lot of time on film sets with my dad at work, and as a kid that’s a very appealing thing, to watch grownups get to play dress-up and pretend that they’re different people — and then get paid for it!”

Credit: Getty Images; Warner Bros.

Having already shown off his creepy acting chops on horror maestro Eli Roth’s Netflix series Hemlock Grove, Skarsgard — whose older brother Alexander played a sexy-but-scary creature of the night on HBO’s True Blood — was ready to take on a monster truly out of this world.

“F— yeah,” Skarsgard recalls telling his agent when first asked if he’d like to read for Pennywise, the demonic clown who feeds on children in the fictional New England town of Derry, Maine.

RELATED VIDEO: The Cast Of ‘IT’ Has A Message For Clowns: ‘We’re Sorry If We’re Giving You A Bad Rep’

“I was really excited to do a full character transformation into something that’s so far away from who I am in every way,” he explains. “So I took a lot of time and worked on how Pennywise would sound and move and all that. Things changed along the way, but it was convincing enough that I got the job.”

Between Skarsgard’s own imagination and director Andrés Muschietti’s vision for the character, a modern version of Pennywise, far darker and more modern than Curry’s, was born. “You need to access parts of yourself where you’re thinking, ‘What’s the most disturbing or horrifying thing that could happen right now?’ And then you have to commit to that.”

Gustaf Skarsgard, Bill Skarsgard, Alexander Skarsgard
(L-R) Gustaf Skarsgard, Bill Skarsgard and Alexander Skarsgard.
| Credit: Richard Shotwell/Invision/AP

While he watched the original series as part of his preparation, Skarsgard says, “It was really important to me that I found something that was unique in my interpretation of It. I needed the character to be something new that we haven’t seen before, especially because we were dealing with something people are already familiar with.”

So Skarsgard turned to the book for further inspiration, devouring the nearly 1200-page novel in just 10 days. “When I wasn’t sitting at home reading, I’d be listening to the audiobook while I was out grocery shopping. I was so immersed, it was like binge watching a TV show. Sometimes you watch something so much you start to see it when your eyes are closed.”

As difficult as it was to get into the mindset of a character he describes as “pure evil,” Skarsgard says it was actually harder to let go of the villainous persona after filming than it was to become Pennywise in the first place.

“It was weird,” he says. “I really enjoyed myself doing it, but the day after we wrapped, I went back home to Stockholm, Sweden, and it’s always a weird experience when you work really hard on something and then you go back to regular life at your childhood home.

“And that’s when I finally realized what an impact the character had had on me. For the following two weeks I would have these really disturbing dreams about Pennywise,” he adds with a laugh. “It was very strange, it was almost like a really slow exorcism to completely let go of him.”

Trying to find a suitable analogy for non-actors, Skarsgard offers, “The closest thing I can liken it to is being in a very destructive relationship, because you never really realize you’re in one until you’re out.

“And then as soon as you’re out of it, you’re like, ‘Oh my God, I can see it all so clearly now.’ Doing characters is almost like being in a relationship with a made-up person, and you don’t really see the journey clearly until it’s over.”

In the novel, Pennywise awakens from Derry’s sewers every 27 years to feed on children, but Skarsgard won’t have to wait much longer before the clown comes back for him.

Despite the bad dreams, Skarsgard says, “I did have so much fun with the character, and I’m really looking forward to getting back under that clown makeup for the sequel.”

It floats into theaters Friday.