The ER Character You Forgot It's Always Sunny In Philadelphia Star Glenn Howerton Played

The narrative around the start of "It's Always Sunny in Philadelphia" is that it was a shoestring production held together by three young amateur actors. Co-creators Glenn Howerton, Rob Mac, and Charlie Day were only working with $100 and a dream, and they miraculously turned that dream into a hit sitcom. Furthering this inspiring underdog narrative is Howerton's failed lead role on "That '80s Show," a 2002 attempt to cash in on the "That '70s Show" popularity. The show crashed and burned within a single season, but it wasn't all bad; Howerton reportedly could only afford the professional camera they used for the "It's Always Sunny" pilot because of his paycheck from the canceled series.

But after he starred in "That '80s Show" and before he began "It's Always Sunny," Howerton landed a role on "ER," a hit medical show that reigned on NBC from 1994 to 2009. Howerton's character, Dr. Nick Cooper, popped in for six episodes in early season 10 (which aired in 2003). It was hardly a lead role, and it didn't make him a star yet, but it was still a big deal. It's another reminder that, as ambitious as making their own show from scratch was, the "It's Always Sunny" creators weren't quite as green to the industry in 2005 as many assume. 

Also showing up on "ER" for a bit was Rob Mac, who played a one-off character (a random firefighter) later in the same season as Howerton. Their co-stars Kaitlin Olson and Charlie Day never appeared on the medical show, but at least Day got to play a one-off bad boy character in a 2001 episode of "Law & Order." The legal drama series seems like a better fit for Charlie than a medical series, given his natural affinity for bird law.

"ER" was one of the first projects Howerton booked after the flop of "That '80s Show," and the role was a notable shift away from comedy. Dr. Nick Cooper is a very serious person dealing with a constant barrage of heavy material; it's the sort of intense, dramatic role Howerton loves to play, but after "ER," he would have to wait almost 20 years before he could do something similar with "Blackberry."

"I never considered myself a comic actor," Howerton revealed in a 2020 interview. "I always loved doing comedy — I guess I could say fairly that I felt like I was pretty good at it — but it wasn't my goal to be in comedy or spend as much of my career in comedy as I have. It just kind of happened."

Elaborating on his "ER" role, Howerton said, "So yeah, this was one of the first things that I did. It was like a six-episode arc, and it was super exciting and also nerve-wracking ... I was at a very insecure point in my career too, where I just felt like, 'I don't know what I'm doing. I don't know how to do this.'" Despite his self-doubt, Howerton's arc on "ER" was clearly a success, to the point where the show extended his character's storyline mid-way through. But even though no viewer had complaints about his performance, the "ER" writers didn't keep him on as a regular. As Howerton explained:

"It's so weird, because when you're a young actor, any job is a really, really big deal. You know what I mean? And it was like, 'wow, I'm gonna do three episodes of ER!' and I was like, 'This is it, man, I've made it!' ... And then it turned into six episodes, and I was like, 'Oh man, they might make me a series regular!' and then they didn't." 

But although Howerton never returned to play a doctor full-time, at least he had the pleasure of playing an EMT in an "It's Always Sunny" episode over 20 years later. Dennis Reynolds may not have been as professional a medic as Dr. Cooper was, but at least he had fun while the gig lasted.