1. Chris Pratt

Before he became a superhero heart-throb in The Guardians of the Galaxy franchise, Pratt played college activist Che Cook in season 4. He memorably sang a song about polar bears for Seth - while completely naked.

2. Max Greenfield

He may be world famous now for playing Schmidt on New Girl, but back in the early 2000s, he played a young Sandy Cohen in a season 4 flashback scene. Years later Peter Gallagher, the actor who played Sandy, was cast to play Schmidt’s dad in New Girl. We see what they did there!

3. Shailene Woodley

In season 1, the Divergent star played the 11-year-old Kaitlin Cooper, Marissa’s sister. Sadly, she was shipped off to boarding school and she returned as an entirely different actress…

4. Willa Holland

The Arrow and Gossip Girl star took over from Shailene Woodley, playing Marissa’s sister Kaitlin from season 3 onwards.

5. Olivia Wilde

She originally auditioned for the role of Marissa and lost out to Micha Barton. But Wilde was cast in season 2 as Alex, Marissa’s girlfriend and manager of The Bait Shop. She has since gone on to star in the TV show’s House, Vinyl and BoJack Horseman.

6. Paul Wesley

Before he was stealing hearts as The Vampire Diaries’ Stefan Salvatore, Wesley played bad boy Donnie who waved a gun around before accidentally shooting Luke at a Newport teen party. We definitely preferred him as Stefan…

7. Kat Graham

Speaking of The Vampire Diaries, Graham (aka Mystic Falls witch Bonnie Bennett) appeared as Ryan’s friend Kim in an episode of season 3. 

8. Jeffrey Dean Morgan

The Walking Dead and Grey’s Anatomy star made a very brief appearance in season 2 as Joe Zukowski, a former friend of Sandy Cohen’s who is in jail for manslaughter.

9. Bella Thorne

Before she became a Disney Channel star and landed a role on our other obsession Famous in Love, Thorne played a young version of Taylor Townsend in a season 4 flashback.

10. Morena Baccarin

In season 3 of The O.C., Baccarin guest starred as Maya Griffin, the daughter of Sandy’s competitor. She went on to star in Homeland, Deadpool and Gotham, where she fell in love with Ben McKenzie aka Ryan Atwood. The couple married in 2017 although McKenzie has said he doesn’t remember her from The O.C. days. 

11. Paris Hilton

At the height of her early-2000s fame, Paris Hilton showed up in an episode of season 1 as a girl the gang met in a bar. She kissed Seth, talked about her grad school thesis and took a selfie with a flip phone. It was epic.

12. Amber Heard 

She now stars in Aquaman opposite Jason Momoa, but back in season 2 of The O.C. she played a sales assistant in a mall that Seth, Ryan, Summer and Marissa got stuck in overnight. 

13. Lucy Hale

You'll probably remember Hale as the star of her own teen drama, Pretty Little Liars. But before she was Aria, she played Kaitlin’s boarding school roommate Hadley in season 3.

14. George Lucas

You know you’ve made it when George Lucas wants to cameo on your show. He appeared as himself in season 2, personally meeting with Seth about turning his comic book Atomic County into a movie. His daughter was a huge fan of the show and he gave creator Josh Schwartz a Storm Trooper helmet as a thank you.

15. Kevin Sorbo

Post Hercules: The Legendary Adventures, Sorbo found his way onto season 4 of The O.C. playing Ryan’s criminal father Frank Atwood. He romanced and won over Julie Cooper in the show’s final season.

16. AnnaLynne McCord

Two years before she landed the role of Naomi Clark in 90210, McCord played a character simply called ‘hot girl’ in season 3. She didn’t have a name, but she caused a lot of drama when she hooked up with Volchok at Marissa’s prom. 

17. T.I.

Before he was famous, the rapper appeared as himself at a spring break pool party in season 2 and performed his hit Bring ‘Em Out.

18. Colin Hanks

After he made his name in Roswell, the younger Hanks played Grady Bridges in the show’s first season. He was the star of The O.C.’s show-within-a-show, The Valley. You can now watch him in Life In Pieces!

19. Steve-O

In season 4, the Jackass star played a marine who forced Seth and the gang to do shots while on holiday in Mexico. That sounds just like something he’d do…

Stream all 4 seasons of The O.C. now!