Celebs Who Had Successful Careers After Guest Starring On ER

With its ridiculously good-looking ensemble cast, shocking twists and turns, highly stylized look, and sexy break-room shenanigans, "ER" ruled the television landscape of the 1990s and early 2000s. It helped to define the new era of prestige dramas and, for 15 seasons, led small-screen viewers on a high-stakes journey.

"ER" was one of the highest-rated shows in TV history, reaching over 30 million viewers a week in the 1990s. The Michael Crichton series did not just make superstars out of its regular cast (hello, George Clooney), it became a place where young actors could get both on-set experience and major exposure. The NBC medical drama needed a new cast of guest stars every week to populate Cook County General Hospital's emergency room. Two aspects made "ER" unique. One was its voyeuristic look into doctors' and patients' personal lives. The other was its distinct visual style with its shaky handhelds, 360-degree spinning camera, and chaotic overlapping dialogue. It all made the show seem so realistic viewers felt that they were right there on the operating table.

Some "ER" patients did not make it, and some then-unknown guest stars went on to be among the most acclaimed actors working in Hollywood. Take a look at some of your favorite actors who popped by Cook County General on their way to Hollywood stardom.

Zac Efron is one of the few teen idols to make the successful transition to adult actor. Before he wowed teenage girls with his chiseled looks and ice blue eyes as Troy Bolton in the "High School Musical" trilogy, Efron played Bobby Neville on a Season 10 episode of "ER" that aired in 2003. It was the actor's second credited role in his filmography. Just a year later, Zac Efron appeared in a Lifetime movie that would be his first starring role. In "ER" though, Efron appeared briefly as a shooting victim.

A few years after the medical drama, Efron landed his breakout gig in the Disney franchise's "High School Musical" films. The actor is truly everything that Disney loves: a clean-cut kid who can act, sing, and dance. When his Disney career wrapped, Efron followed with some teen-friendly movies like the comedy "17 Again." However, it's clear that he also made an effort to take on more mature material, such as the R-rated comedy "Neighbors" in 2014.

Along with crowd-pleasing films like "The Greatest Showman" and "Baywatch," Efron turned to dark roles. He played a couple of real-life characters, like serial killer Ted Bundy in the film "Extremely Wicked, Shockingly Evil and Vile," and took on former professional wrestler Kevin Von Erich in the tragedy "Iron Claw."

Aaron Paul was a working television actor in the early 2000s, guest starring in one-off episodes of "The X-Files," "NYPD Blue," and "CSI: Crime Scene Investigation." He worked his way over to the set of "ER" in 2003 for a Season 9 episode called "A Saint in the City." In his single episode of work on the medical drama, Paul played a teenager named Doug, laden with a nose ring and other face piercings, who was tasked with looking after his sick mother and taking care of his younger siblings. 

Following "ER," Paul continued working as a guest star on different TV shows like "Veronica Mars" and "Ghost Whisperer." He also scored small roles in big movies like "Mission: Impossible III." Paul's big break finally came in 2008 when Vince Gilligan cast the actor on the AMC drama "Breaking Bad." He played fan-favorite Jesse Pinkman, a drug dealer who teams up with his former chemistry teacher, Walter White, to make high-grade meth. 

Before White turns heel, going from "Mr. Chips" to "Scarface," Pinkman seemed like a hapless dope fiend destined for prison. But in the end, it is Pinkman who becomes the moral center of the acclaimed show's five seasons. Paul went on to reprise the role in 2019's feature film "El Camino." The actor has also appeared in several other projects, including HBO's "Westworld," and as a voice actor on Netflix's long-running animated show "BoJack Horseman."

Nick Offerman's first official TV credit came playing Rog in the Season 4 premiere of "ER" in 1997. The installment is known as the show's only live episode. It was shot twice for both the East and West coasts. In "Ambush," Offerman played a rocker who takes his band's bass player to the emergency room. 

Offerman may have had a bit part on the medical drama, but he did get to mix it up with the show's matinee idol, George Clooney. "They had a huge pot of soup going backstage, it had this maritime feel like we were building a boat or something, instead of a show," he told "People TV's Couch Surfing" (via Entertainment Weekly). "And Clooney and I found ourselves eating soup backstage and we said, 'I feel like we're sailors.' And we started singing 'The Wreck of the Edmund Fitzgerald' by Gordon Lightfoot." Offerman added that he saw Clooney years later at an Oscar party, and he remembered their harmonious on-set moment.

Offerman is best known for playing Pawnee's favorite libertarian, Ron Swanson, on the workplace sitcom "Parks and Recreation" over seven seasons. However, it was Offerman's against-type turn as survivalist Bill in HBO's drama "The Last of Us" that made the world see the rugged actor in a new light. Offerman earned the Emmy for Outstanding Guest Actor in a Drama Series in 2024 for his unforgettable, single-episode performance as a man who falls in love with another man in a post-apocalyptic world.

Chris Pine's first IMDb credit came on "ER" in a 2003 episode titled "A Thousand Cranes." In the Season 9 installment, Pine played a drunk teenager who shows up at the emergency room following a five-day party. "It was really neat, you felt like you were a part of a team and coming up with how they were going to do it ... It was very memorable," Pine told IMDb about his experience on the series. 

Pine has gone on to have an incredible career on the big screen. Perhaps the actor's most well-known role came playing Captain Kirk in J.J. Abrams "Star Trek" reboot for three films, "Star Trek," "Star Trek Into Darkness," and "Star Trek Beyond." One major franchise was not enough for the actor, who also starred as Captain America in three standalone movies and multiple "Avengers" installments. He also co-starred in two "Wonder Woman" movies as Steve Trevor. 

Despite the blockbuster credentials, Pine has also taken on critically acclaimed dramatic roles. He played a criminal in the neo-western "Hell or High Water" and even showed off his comedy chops in 2015's "Wet Hot American Summer: First Day of Camp." He also directed and starred in the 2023 neo-noir "Poolman."

Adam Scott may be a pro now, but he messed up big time during his guest spot on "ER." The "Severance" actor appeared on a 1995 episode called "Full Moon, Saturday Night." It was one of Scott's first roles. In 2025, a clip featuring Scott and "ER" star Noah Wyle worked its way around social media. 

Scott talked to Decider about how he blew a long take, an extended shot with no edits. "There was a long take of me being wheeled in through the entire ER as Noah Wyle and [Sherry Stringfield] have dialogue above me," said Scott. "And we went through the whole thing. They got their lines perfect. Everything was great," he added. "Except I had taken my breathing thing out of my nose and had forgotten to put it back in."

Thankfully for Scott, the mistake did not have an effect on his career. He went on to co-star in several hilarious TV comedies like "Party Down" and "Parks and Recreation." However, Scott is also an outstanding dramatic actor, as seen in "Big Little Lies" and his starring role in the mind-bending Apple drama "Severance." The actor received four Emmy nominations for his work on the Ben Stiller series. Additionally, he may only have a small role in the comedy "Step Brothers," but his turn as the smug villain Derek Huff and his family's polished a cappella version of "Sweet Child O' Mine" nearly stole the film.

Octavia Spencer appeared in one episode of "ER" called "Hazed and Confused." The Oscar winner played a pregnant woman named Maria Jones in the 1998 Season 5 installment. Jones faked stomach pain in order to get a scan so she could see whether she was having a boy or a girl.

Spencer has proved to be one of the most versatile performers in Hollywood. By the mid-2000s, she became an in-demand character actor. However, it was her breakout performance in the 2011 drama "The Help" that took her to the next level of fame. The actor won the Academy Award for Best Supporting Actress and cemented her legacy in Tinseltown. From there, Spencer worked on hard-hitting dramas like "Snowpiercer" and "Fruitvale Station." She was again recognized by the Academy in the 2010s with Oscar-nominated performances in "Hidden Figures" and "The Shape of Water."

But Spencer has serious comedy chops as well. She more than held her own playing with comedy titans like Melissa McCarthy in the superhero parody "Thunder Force" and Will Ferrell in "Spirited." The actor has also dropped in for scene-stealing guest spots on small-screen comedies like "30 Rock" and "Running Point." Spencer worked with Allison Janney on "Mom," where rumors forced us to ask what is the truth about Allison Janney and Octavia Spencer's relationship. Spencer also works as a producer. She served as executive producer on the Oscar winning film "Green Book" and co-executive producer on the drama "Fruitvale Station."

The acting role Christina Hendricks says she regrets is not her character Joyce Westlake from Season 8 of "ER." Her memorable four-episode arc in 2002 centered around Westlake's relationship with her abusive husband. "ER" doctor Abby Lockhart is neighbors with Westlake and tries to get her to leave her husband. Hendricks was just getting her feet wet in the biz when she got the call from showrunner John Wells. "I remember exactly where I was when I got the call that I was going to be doing four episodes [of 'ER'], and I started crying in the car, because I was so happy," Hendricks told People.

The Emmy Award nominee was happy to get to work with TV veteran Maura Tierney, who played Lockhart. "I do remember asking [Maura], 'How do you get yourself up to this place to cry and go through this emotion?'" she added. "And she goes, 'I really believe that I'm in it. I have to sit there and believe that I'm really in it.' And I went, 'Okay. Okay, that's what I'll do.'"

Following "ER," Hendricks continued to work steadily as a guest star. She would finally break out in 2007 when she landed the role of Joan Holloway Harris in AMC's prestige drama "Mad Men." The actor earned six Emmy nods for her performance as the glamorous but tough-as-nails office manager turned partner at Sterling Cooper. 

Well before traveling to a galaxy far, far away, Ewan McGregor guest-starred in a Season 3 episode of "ER" called "The Long Way Around." Select American audiences already knew McGregor from his performance in "Trainspotting." However, millions more "ER" fans got a look at the actor because the medical drama was one of the highest-rated shows in TV history, reaching over 30 million people a week in the 1990s. The Scottish actor played Duncan Stewart, who robs a convenience store where Carol is shopping. The robbery goes off the rails as Stewart loses control and turns the ordeal into a hostage standoff. McGregor earned an Emmy Award nomination for his memorable performance. 

The actor worked steadily over the next three decades, so Ewan McGregor is worth more than you'd expect. Following "ER," McGregor kept an indie-minded career with starring roles in "A Life Less Ordinary" and "Velvet Goldmine." In 1999, he took on Obi-Wan Kenobi in the "Star Wars" prequel trilogy. 

But it wasn't all lightsabers and starships. McGregor showed off his vocal range in Baz Luhrmann's jukebox musical "Moulin Rouge!" He also appeared in "Black Hawk Down," "Big Fish," and "The Ghost Writer." Then, McGregor made an impressive return to the small screen. In 2017, he was nominated for his second Emmy Award for playing twin brothers in Season 3 of "Fargo." McGregor finally won his Emmy in 2021 for his titular performance in the limited series "Halston."

Every actor has to start somewhere, for Eva Mendes it was on a Season 4 1998 episode of "ER" called "Exodus." She played Donna, a concerned babysitter who brings a sick child into the ER for treatment. 

Mendes' breakout role came a few years later in the 2001 crime drama "Training Day," where she played the girlfriend of Denzel Washington's character. Then, the Cuban-American actor's career took off as she co-starred in a string of Hollywood blockbusters, such as "2 Fast 2 Furious" and "Hitch." But Mendes wasn't all about fast cars and romance. She showed her impressive comic range opposite comedy legend Will Ferrell in 2010's "The Other Guys."

Mendes also dabbled in more complex, edgier non-traditional films like "Bad Lieutenant: Port of Call New Orleans." In 2012, she met her future husband, Ryan Gosling, on the gritty independent film "The Place Beyond the Pines." Mendes and Gosling played a couple with an infant son, and their chemistry was so electric it jumped off the screen. Why Eva Mendes disappeared from Hollywood after 2014 is mainly because she had children with Gosling. "Your career comes and goes but kids, yeah, that was easy for me," she told People about her decision to take a break from acting. "They're just formative years. I wanted to be there for all of it."

Kristin Davis made a quick appearance in a Season 1 episode of "ER" called "Luck of the Draw." In the 1995 installment, she played Leslie, a concerned aunt who brings her niece into the ER after she suffers a bee sting. However, Leslie is mostly interested in flirting with the handsome Dr. Ross, played by George Clooney.

Following her single episode appearance on "ER," Davis took a manipulative villainous turn on "Melrose Place," in Season 3 of the soapy drama. The real reason Kristin Davis left "Melrose Place" has a lot to do with her conniving character. "Seinfeld" fans may recognize Davis from a 1997 episode where she played Jerry's girlfriend, Jenna — Jerry accidentally knocks Jenna's toothbrush into the toilet. Most people know Davis from her star-making role as Charlotte York in "Sex and the City." The HBO series ran from 1998 to 2004 over six fashion-filled, brunch-loving, cosmo-sipping seasons. Inside Carrie Bradshaw's tight friend circle, Charlotte, an optimistic and hopeless romantic, played the prude to the vixen Samantha. Davis reprised the beloved character for two "Sex and the City" movies and the revival series "And Just Like That..."

Davis has a packed filmography outside of "Sex and the City." She's appeared in several holiday films and taken on roles in movies like "Couples Retreat" and "Journey 2: The Mysterious Island." The actor also did voice work on the animated series "Miss Spider's Sunny Patch Friends."