26 Celebrities You May Not Have Realized Guest-Starred On 'ER'

There is an endless list of huge stars who have guest-starred in various episodes of the show.

Stephanie

• Published in Interesting
• May 29, 2022

ER was undoubtedly the medical drama of the nineties. In fact, the popular television series remained prevalent right up until 2009, when it finally wrapped up after fifteen seasons and 331 episodes.

It's the second-longest-running medical drama in American TV history, with Grey's Anatomy being the first. Set in the fictional Country General Hospital in Chicago, we've watched as our favorite characters faced critical medical situations in every episode.

Starring none other than George Clooney, Noah Wyle, Maura Tierney, and Julianna Marguiles, to name just a few, the show was able to keep our attention for fifteen years. But, along the way, many celebrities also guest-starred in the series.

From Zac Efron to Kirsten Dunst to Shia LaBeouf to Ewan McGregor, there is an endless list of huge stars who have guest-starred in various episodes of ER. And we're willing to bet that you never even realized most of these big names appeared in the show!

We thought it would be fun to look back at some of the biggest celebrities to ever have had a guest role on one of the biggest television dramas of our time. So, keep scrolling to take a look through 26 celebrities you never knew guest-starred on ER.

1. Shia LaBeouf

The Transformers star played Darnel Smith in episode 12 of season 6. His character suffered from muscular dystrophy.

2. Chris Pine

Before making it big, Chris had a small role in ER episode 16 of season 9. He played an alcoholic named Levi.

3. Zac Efron

Before he became the object of every teenage girl's affection in Highschool Musical, Zac Efron guest-starred on ER. In episode 3 of season 10, Zac played Bobby Neville, a young boy who had been shot.

4. Ewan McGregor

Shortly after his role in Trainspotting, Ewan guest-starred in ER. In episode 15 of season 3, Ewan played a liquor store burglar.

5. Josh Peck

Josh guest-starred in ER before he became a star in Drake & Josh. In episode 13 of season 7, he played a teenager who went to the ER needing a heart transplant.

6. Rooney Mara

Before starring in The Girl With The Dragon Tattoo, Rooney had a small part in ER. In season 15, episode 19, Rooney played Megan, a young woman struggling to give up her baby.

7. Kristin Davis

Before becoming Charlotte on Sex And The City, Kristin guest-starred opposite George Clooney in ER. In episode 13 of season 1, Kristen played a woman who brings her niece to the emergency room.

8. Lucy Liu

In season 2, episode 3 of ER, Lucy played the mother of a little boy with AIDS. Later, she went on to star in Charlie's Angels and Ally McBeal.

9. Tobin Bell

Before traumatizing us all as Jigsaw in the Saw movies, Tobin had a brief role in ER. In season 1, episode 2, he played a bossy hospital administrator in the medical drama.

10. Ariel Winter

In episode 15 of season 15, Ariel guest-starred on ER as Lucy, a young girl whose mother had emergency surgery after an accident. Of course, Ariel later went on to star as Alex Dunphy on Modern Family.

11. Michael Cudlitz

Before becoming Abraham in The Walking Dead, Michael appeared in season 2, episode 16 of ER. He played a wounded fireman.

12. Adam Scott

More than ten years before he became a star in Parks and Recreation, Adam guest-starred in episode 20 of season 1 of ER. He played David, who had been hit by a car.

13. Gabrielle Union

Gabrielle played Tamara Davis, a high school student who crashed into a telephone pole. Gabi's guest role in ER was in season 6, episode 2.

14. Chadwick Boseman

Before the late star became Black Panther, he appeared in an episode of ER. In episode 6 or season 15, Boseman played a man named Derek, who was a boxer and went to the emergency room after a rough fight.

15. John Hawkes

Long before he became an Academy Award nominee, Hawkes guest-starred in ER. In episode 1 of season 4, he played a production assistant filming a documentary at Country General.

16. Cara Buono

The Stranger Things star appeared in episode 22 or season 15 of ER. She played a new mother in the series finale.

17. Kirsten Dunst

In season 3, episode 5 of ER, Kirsten played a homeless teenager named Charlie. Kirsten was already a star at that time, having starred in Interview With The Vampire and Little Women.

18. Deborah Woll

We fell in love with this fiery redhead when she starred in True Blood as Jessica. But before that, she played a young nurse in ER season 14, episode 14 named Aurora Quill.

19. Stana Katic

Before starring in Castle, Stana guest-starred in ER episode 4 of season 12. She played a patient who woke up suddenly after being in a coma for several years.

20. Josh Hutcherson

Before starring in the Hunger Games with Jennifer Lawrence, Josh had a guest role in ER. In episode 8 of season 9, he played Matt, a boy who was hit by a drunk driver.

21. Josh Radnor

Before Josh made us laugh in How I Met Your Mother, he played a far more serious role in ER. In season 9, episode 17, Josh played a man who was being treated for an allergy to penicillin.

22. Eric Stonestreet

Before making us laugh in Modern Family, Eric played a rather interesting character in ER. In episode 3 of season 7, Eric played Willie, who ended up in the ER after cutting his ears, attempting to make them look like Spock.

23. Aaron Paul

Before becoming Jesse Pinkman in Breaking Bad, Aaron appeared in ER. In episode 12 of season 9, he played a teenager who became the carer for his younger siblings when their mother became ill.

24. Eva Mendes

Long before Eva starred in films like Hitch and Training Day, she guest-starred on ER. In episode 15 of season 3, she played the babysitter for a little girl with an E.coli infection.

25. Kat Dennings

Before becoming the cheekiest waitress in history in 2 Broke Girls, Kat had a guest role in ER. In season 12, episode 5, Kat played Zoe, a young woman who has a fling with Dr. Barnett before revealing that she's only 14 years old.

26. Nick Offerman

Long before he starred in Parks and Recreation, Nick played Rog in an episode of ER. In episode 1 of season 4, Nick's character rushed his best friend named Boz to the emergency room.

So, there you have it. 26 celebrities you never knew guest-starred on ER.

Are we right? Or did you already know about some of these impressive guest stars?

We loved ER for so many reasons, and this list of celebrity guest stars only adds another layer to the show's appeal. We would love to hear your favorite ER memories in the comment section below.

Stephanie