From the moment it debuted with a two-hour pilot episode in September of 1994 until it left the air in 2009, ER was a ratings monster. It regularly topped the ratings for the year during its 331-episode run and launched careers left and right. George Clooney for goodness sake! Not only did it have big stars in its regular cast like Clooney, Anthony Edwards, Maura Tierney, and Eriq LaSalle, but it also had a huge amount of guest stars and up-and-coming actors roll through the show. Here is our list of some of the biggest.
Nick Offerman
Nick Offerman is most well known for playing the great Ron Swanson on Parks and Recreation where he regularly delivered some of the funniest lines on the show. He didn't have anything funny to say in his one role on ER where he played a bandmate of a bass player in distress in the emergency room.
Taraji P. Henson
The accolades for Taraji P. Henson's acting have come fast and fierce in recent years, but she's been showcasing her talent on screen since the late '90s. One of her earliest roles was in a Season 4 episode of ER, and then in Season 5, she returned in a different role. She kept landing guest roles for years on shows like CSI and Boston Legal before landing her starring turn in Empire and the rest is history.
Bradley Whitford
A few years before the role of Josh Lyman on The West Wing would make him a star, Bradley Whitford appeared in two episodes of ER in 1995. He'd been working regularly for almost a decade at that point and would find small roles here and there for another few years before The West Wing. He's been an in-demand actor ever since.
Kristin Davis
Before she was a regular on Melrose Place, and before she was one of Jerry's many girlfriends on Seinfeld, Kristin Davis played a woman who was very into George Clooney's character very briefly in one episode of the first season of ER. While she only showed up once on the show, it clearly opened some big doors - and big martini glasses - in the future.
Zac Efron
Before becoming a star in High School Musical, Zac Efron was almost type-cast as a troubled teen. On ER he played a teenager who turned up in the emergency room after being shot. He was also a troublemaker in an early role on NCIS. These days he's one of the biggest stars to grace the screen, but he used to just be in trouble on screen!
Ewan McGregor
Ewan McGregor is something different to different generations. For some, he'll always be Renton in Trainspotting. Of course, for many, he'll always be a young Obi-Wan Kenobi. For even others, he's known as the guy who drove his motorcycle around the world in Long Way Round. You can't help but wonder if that name was inspired by his guest spot on ER in a Season 3 episode called "The Long Way Around" in 1997.
Julie Bowen
While Julie Bowen is best known these days for playing Claire Dunphy in Modern Family, her career stretches way further back. Her first TV role came in the early '90s and her breakout role came in the 1993 Adam Sandler smash hit Happy Gilmore. In the late '90s, she had a nine-episode run on ER as the reoccurring character named Roxanne Please, who was John Carter's (Noah Wyle) girlfriend.
Ving Rhames
1994 was a big year for Ving Rhames. Not only did he star in Pulp Fiction, but he also landed a reoccurring role as Walt Robbins, father-in-law to Dr. Peter Benton (Eriq La Salle). In total, he appeared in eight episodes over three seasons, but by then he'd also starred in Mission: Impossible and the rest is history.
Lucy Liu
Lucy Liu is no stranger to hit television shows. She was a star of Ally McBeal in the '90s and '00s, and in Elementary in the teens. Early on, she also appeared in cameos and supporting roles on big shows like NYPD Blue and The X-Files. She also made it onto three episodes of ER, in 1995.
Chris Pine
Believe it or not, there was a time when Chris Pine wasn't one of the "Chrises" and wasn't one of the biggest movie stars in the world. He was, in his early days, just like so many other actors, just looking to snag any role they could. Luckily for Pine, it was on a show like ER. In fact, the show he appeared in during Season 9 of the show was his first credited acting performance.
Don Cheadle
When Don Cheadle appeared as a doctor in a 4-episode arc in 2002 on ER, he was already well-established as an actor. In fact, it came not long after he was established enough to take his name off the credits of Ocean's Eleven, despite delivering some of the best one-liners in the movie.
J.K. Simmons
Any fan of Law & Order knows just how ingrained J.K. Simmons was in prime-time television around the turn of the century. He was a regular on that show, and he turned up in a bunch of others as well, including an episode of ER in 2004. you can always count on a great J.K. Simmons performance, no matter what he is in.
Christina Hendricks
While she had been cast in a number of shows before Mad Men, Christina Hendricks had never really broken through as a star. That changed with the AMC show, but before that, she was just a regular hard-working actress in Hollywood. One of her earliest gigs was on ER in 2002.
Adam Scott
Adam Scott is not the only Parks And Recreation star to appear in ER early in his career, but he did have a pretty intense role as an injured man clinging to life in the emergency room way back in 1995. It's hard to imagine it took 15 more years to get the big-time attention he deserves when he landed his role on Park & Rec.
Glen Howerton
In 2005 Always Sunny In Philadelphia took the world by storm and went on to become one of the longest-running sitcoms of all time. Glen Howerton played a huge part in that, as one of the stars and co-creators. A couple of years earlier, he was playing a very different role as a doctor in six Episodes of ER during its 10th Season.
Keiko Agena
Gilmore Girls regular and co-star of Prodigal Son, Keiko Agena is one of the few actors who played two different characters on ER. She first appeared on the show very early in her career, in 1998, then later appeared in the final season in 2009.
Jessica Chastain
With three Oscar nominations and one win, Jessica Chastain has proven she's among the best Hollywood has to offer. She proved her acting years ago though, in shows like ER. In only her second credited role, she appeared on ER in 2004 in an episode called "Forgive and Forget."
Aaron Paul
For most people, Aaron Paul is best known for his legendary role in Breaking Bad but years before that show would become a hit, he played a pretty similar character on ER in an episode called "A Saint in the City," way back in 2003.
Octavia Spencer
In 1998 when Octavia Spencer appeared on ER, it was the latest in a string of supporting roles she landed early in her career. That string would continue for a little while longer before she emerged as one of the most beloved stars of the teens and '20s after her star-making role in The Help.
Mena Suvari
As it was for a lot of cast members, American Pie was huge for Mena Suvari. She had been working for a few years in Hollywood before that, picking up roles here and there in shows like Boy Meets World and movies like The Slums of Beverly Hills. Another early role came in a 1998 episode of ER where she played a high school cheerleader who didn't want to listen to her doctors.
Kirsten Dunst
As a child actor, Kirsten Dunst's career started when she was just six years old. It would be a few years before she landed a brief reoccurring role as a troubled teen in six episodes of ER in the show's third season.
Dakota Fanning
Quite a few child actors who went on to greater fame came through the doors of the emergency room at Cook County General Hospital, including a young Dakota Fanning. Fanning played a young girl named Delia who came in after a car accident and viewers find out she's a cancer survivor.
James Cromwell
One of the ultimate "that guys" in Hollywood, James Cromwell has been acting for decades. His career really started in earnest in the mid-'70s and he's been playing supporting and starring roles ever since. On ER, he played a drug-seeking priest in four episodes in Season 7.
Josh Peck
Josh Peck was a breakout Nickelodeon star as half of Drake & Josh. That wasn't his first role though. After a few small roles and a reoccurring spot in The Amanda Show (which led to Drake & Josh), he landed a small role in an episode of ER in 2002 as a kid with heart problems.
Eva Mendes
Before Eva Mendes semi-retired to raise her family with Ryan Gosling, she was one of the biggest stars on the planet. You can trace her career all the way back to her very first role which came in 1998 on an episode of ER. It's wild to look back and watch her doing her first on-screen performances with George Clooney and not think about what lay ahead for both of them.
Shia LaBeouf
Without a doubt, Shia LaBeouf has had one of the wildest careers of the 21st Century. There have been times when he was on top of the world, and others when he... definitely wasn't. One high point early in his career was of a kid in the emergency room of Cook County General in 2000, during Season 6.
Milana Vayntrub
Milana Vayntrub eventually became one of the most recognizable actors in commercials as the AT&T pitchwoman. Long before that though, she was like a lot of child actors who got their start on ER. She appeared in three episodes, her first three credited roles, as a Russian girl, way back in Season 1.
John Mahoney
Before scoring the role of a lifetime as Martin Crane on Fraiser, John Mahoney had been a steadily working actor going back to the '70s. After Frasier, he could pretty much write his own ticket. One role he chose to take was that of a self-professed "drag queen" whose long-time boyfriend was in rough shape in the hospital on ER in 2006, making a strong statement about gay marriage before many were brave enough to join him.
Janel Moloney
One of the many great actresses who found early work in their career on ER was Janel Moloney. Moloney scored only a handful of roles between that and The West Wing, but boy was the West Wing lucky to have her - as was ER in its first season when she appeared in one episode.
Amy Ryan
One of the most underrated characters in The Wire has to be Beadie Russell, played by Amy Ryan. About a decade before she joined The Wire in Season 2, she starred in a single episode of ER in the show's first season. She's been in many TV shows and movies since, including a beloved recurring role on The Office and in the underrated Netflix original Worth.
Rosemary Clooney
George Clooney isn't the only famous person in his family. His aunt is, of course, the inimitably Rosemary Clooney, who was one of the most beloved singers of her generation. She only had about a dozen acting credits on her impressive resume, but one was ER during the show's first season. What a great experience for her and her nephew. Her son, actor Miguel Ferrer, also appeared in an uncredited role in the series premiere of the show.
Dan Hedaya
If you grew up in the '90s, Dan Hedaya was seemingly everywhere, but he's probably best remember by that generation as Cher Horowitz's angry but loving father in Clueless. On ER, he plays a lawyer with... questionable ethics, but a heart of gold. He appeared in four episodes over the length of the whole show. remembered
