"It was very surreal to me, reading [the script]. I'm looking at my innocent, newborn son," Denman tells The Hollywood Reporter of preparing for the audition, which he booked while the family was still at the hospital.

There's good reason Brightburn would resonate with the new dad. The tale from screenwriters Brian and Mark Gunn centers on a rural Kansas couple (Denman and Elizabeth Banks) who discover an alien baby in a field. As the boy grows older, the adoptive parents slowly realize that unlike Clark Kent, their son Brandon (Jackson A. Dunn) was not sent to Earth for good.

When Denman read for the role, the Brightburn team saw the actor draw from his emotions as a new father.

"There was so much to channel from, because it's such a horrible thing to confront. What if your child was bad?" says the film's director, David Yarovesky. "He really blew me away in that audition. I couldn't believe how intense it got."

Denman's Brightburn origin story dates back to his days on NBC's The Office, in which he played warehouse worker Roy Anderson, the ill-suited fiance of receptionist Pam Beesly (Jenna Fischer). Denman got to know filmmaker James Gunn, who was married to Fischer at the time and would go on to produce Brightburn and direct the Guardians of the Galaxy movies. They'd go to dinner during the Office years and Gunn would come to see Denman in plays.

"He's someone I've always looked for an opportunity to work with, and I remember selling him to [Banks] early on," recalls Gunn.

Back to The Office: Denman was a fan of the British version and begged his then-agent to get him an audition. He landed the part of Roy, the guy meant to keep Romeo and Juliet apart — or at least, the guy who would keep Jim (John Krasinski) and Pam apart.

NBC's The Office ran from 2005-2013 and remains a dominant force on Netflix. Jim and Pam have become the platonic ideal for TV romance, while Roy remains the poster child for the inattentive romantic partner.

Among the most picked-over quotes about The Office comes from Fischer, who has told an innocuous anecdote over the years in which she noted that the part of her that is Pam loved the part of Krasinski that is Jim, as she explained in 2013 on NPR's Fresh Air: "It is the strangest thing to have a long-term fictional love interest. It's a type of relationship that is very intimate, and it's very powerful, but it's fictional. I mean, there is a part of me that is Pam, and there's a part of him that is Jim, and that part of me is in love with that part of him. But in real life, we are just friends."

In 2016, the actress was asked about her chemistry with Krasinski on Bravo's Watch What Happens Live and explained it similarly, but this time Office fans — perhaps unfairly — seized upon a portion of the quote in which she said a part of her and a part of Krasinski were "genuinely in love." Krasinski was asked about it in an interview, and he suggested the quote was taken out of context, prompting even more headlines.

Denman remembers the story, and thinks it was blown out of proportion. He even notes that at least early on, he and Fischer may have been closer friends than Krasinski and Fischer. (As an Office fan, I must throw in a joke here: Isn't that totally what Roy would say?)

"Jenna and, I we got along really well. I think we may have even got along better than her and John did at the beginning of the show. We would hang out together, we would work out together sometimes. Our lives intersected quite a bit," says Denman.

The Office ran for nine seasons, and Denman was written out of the series after season three. Ahead of what would be his final run, it wasn't totally clear he'd be exiting the show. During contract negotiations ahead of season three, NBC offered the actor a rich deal that would kick in should he be asked to continue for season four. Denman's then-agent told the actor that the writing was on the wall: NBC was offering big money for a hypothetical season four to keep him under his old contract for one more year. He'd never see that money.

Denman understood, but perhaps part of him held out hope there would be a future for Roy. Season three began with Pam and Roy broken up, but Jim was gone, too, having transferred to the Stamford, Connecticut, branch. Roy, meanwhile, cleaned up his act and briefly won Pam back during the season.

"We'd been leading that third season, maybe Roy and Pam will get back together," recalls Denman.

But then came a fateful table read with the cast and showrunner Greg Daniels.

"All of a sudden, Roy was an idiot again. And I went, 'Uh. We're definitely not going to get back together,'" recalls Denman. "At that same table read, we found out The Office has been picked up for three years. Everyone is going, 'Oh, my God! It's amazing!' And I turned to Greg and I go, 'I'm not going to be on this, am I?' And he goes, 'No. It's not you. Honestly. I need to get Romeo and Juliet together, and I can't really do that with you lurking around.'"

Denman asked if he could start looking for other work and Daniels agreed, something the actor remains grateful for. He toplined a pilot that wasn't picked up, but it did give him some career heat and helped land him a new agent. He'd also occasionally return to The Office, most notably in a season-nine episode titled "Roy's Wedding," which revealed Roy was a changed man: successful, sensitive and attentive to his wife — all things that added to a rocky patch Jim and Pam were going through.

"I found out a lot of the times I came back, Krasinski was fighting to have Roy come around. He wanted to mix up things, create more tension and more conflict and stuff," says Denman.

He and Krasinski would work together again in 2016's 13 Hours, Michael Bay's war drama about the 2012 attack on the U.S. diplomatic compound in Benghazi. Denman landed the role after being cast in Tim Burton's Big Fish by casting director Denise Chamain, who worked with Bay.

"I knew that he had a deadpan sense of humor that Michael Bay would appreciate,” says Chamian. “We wanted actors whom audiences had not seen in military roles before but were believable as highly trained soldiers. David nailed the character at his first audition. He was soulful and funny."

In Bay, Denman found a director who loved spectacle but was perhaps not as enthused about the human moments — the scenes with the guys just hanging out, busting each other's chops.

"On 13 Hours, we saved all of those scenes for the last week and those were — as actors — our favorite scenes to do. Bay got through them. I won't say he loved them, but he got through those days and then got back to blowing stuff up," Denman says with a laugh. "I really liked Michael. He really is a big kid. He likes to excite people and make people go 'wow.'"

13 Hours also continued a trend of Denman accidentally injuring Krasinski, following in the steps of the season-one episode of The Office, "Basketball," in which Denman elbowed his co-star in the face — drawing real blood.

"We were doing training and we were firing all these guns. He was sitting next to me and the shell comes flying out and they are hot. Sure enough, my shell landed on his neck and burned his neck," says Denman with a laugh. "Every time I'm around this guy, I'm hurting him! It's not personal."

When it came to joining Brightburn, Denman's Office past came back once more in the form of Gunn, who had kept in touch with the actor over the years and who had invited him to audition for Guardians of the Galaxy Vol. 2 a few years earlier. Banks had approval of her onscreen husband, but says it was a no-brainer to bring Denman aboard.

"We were on the same page about parenting Brandon and how we were going to come at it from different perspectives and whether we were going to stay a team," says Banks. "It was really interesting to build the family together with him, and with Jackson."

Denman's everyman quality helped make his Brightburn character Kyle an avatar for the audience, as he's the one who first accepts that his son must be stopped.

"David did such a fantastic job of taking the audience on this absurd and horrific ride," says Brightburn executive producer Simon Hatt. "He has my favorite line in the movie where he acknowledges, for the first time, just how insane the journey has been and says, ‘What are we going to do next?! Tell someone that we found our son in a spaceship in the woods?!'"

Since opening over the weekend, Brightburn has made more than $17 million globally against a $6 million budget and could spawn a larger universe.

It's a success that comes 20 years after Denman got his first break in Hollywood, when he was cast in the Keanu Reeves football film The Replacements. Looking back, he is proud of the career he has charted, of being recognized by kids on the street as Roy but also maintaining his anonymity, too.

"I always liked being under the radar and sort of having a blue-collar acting career, which is what I envisioned and hoped for," says Denman. "For 20 years I've been doing this. And luckily — knock on wood — I haven't had to do anything else."

— Patrick Shanley contributed reporting to this story.