Glenn Howerton: ‘I’ve always been fascinated by egotistical characters’

Glenn Howerton knows his way around self-involved characters.

He’s currently pulling double duty starring as sociopathic Dennis Reynolds on “It’s Always Sunny in Philadelphia,” and as disgraced Harvard scholar turned teacher Jack Griffin on Peacock’s “A.P. Bio.”

“I’ve always had a fascination with characters who have very large egos,” Howerton, 44, tells The Post.

“I find people who are extraordinarily narcissistic tragic, quite frankly. And the tragedy of it is funny, to me.”

“A.P. Bio,” now in its third season, is a comedy following Jack after he loses his Ivy League dream job to his rival Miles (Tom Bennett) and must reluctantly take a position teaching high school biology in Toledo, OH. There, he uses his students for revenge schemes on Miles and for personal betterment — while Principal Durbin (Patton Oswalt) struggles to maintain order.

But Season 3 sees his attitude shift slightly.

Glenn Howerton in “A.P. Bio.”Evans Vestal Ward/Peacock

“It was important to me that you can see him warming to the students and the teachers,” says Howerton. “There’s a fine line between being an unlikable jerk and a likable jerk. That’s the line that I’m trying to ride with this character, and it’s quite true to the situation — which is that I think he’s starting to like these kids. But he wants to be this Harvard intellectual, and he’s terrified that he’s really just a hometown boy from Toledo. If he admits too much that he likes this place, he starts to skew more towards the ‘I’m just an average guy.’”

The show has had a tumultuous journey, initially airing on NBC before it was axed after two seasons in May 2019. One month after its cancellation, Peacock picked it up for a third season.

“I don’t expect anything that I ever do to be a giant hit, just because I feel like my comedic sensibilities are strange…But the thing that was frustrating about this was that the show was doing so well on Hulu, I was going, ‘Our audience is a streaming audience,’” says Howerton. “Hulu was like, ‘If NBC’s not [making] it, we’ll syndicate it,’ but they didn’t want to finance it. We had this huge streaming audience and nowhere to put [the show].”

But when NBC streamer Peacock set its line-up for original programming, “A.P. Bio” was able to continue.

Rob McElhenney as Mac and Glenn Howerton as Dennis in “It’s Always Sunny in Philadelphia.”Patrick McElhenney/FXX

Meanwhile, Howerton’s other role as Dennis Reynolds is still on the horizon, as long-running sitcom “It’s Always Sunny” has been renewed through Season 15 on FXX, even though the pandemic has made it unclear when that will go into production.

Rumors were circulating that Howerton would depart the series, which he also executive produces and writes, but he has no plans to leave, he says.

“A few years ago, I made the decision to step away from ‘Sunny’ and it was just a personal thing… After 12 years of spending 7-10 months of my year doing one thing, I started to feel a little bit of resentment that it was taking me away from doing other things. And I was like, ‘I shouldn’t be feeling this way about my own baby, my own co-creation.’

“Then [Rob McElhenney and Charlie Day] were like, ‘We can’t figure out how to write you out of all ten episodes, would you be willing to come back?’ and I was like, ‘Just an actor? That’s the most fun part!’ And I got roped back in. I spent two years not really in the writers’ room. My intention is to go back next season and be full-time.”