Summary

• The O.C. remains a favorite after almost 20 years due to its strong character arcs, comedic moments, and important life lessons.
• Chris Pratt, Olivia Wilde, and Amber Heard were all relatively unknown actors when they appeared on The O.C., but they later became big stars.
• The show also featured cameos from well-known celebrities like George Lucas, Paris Hilton, and Steve-O, adding to its popularity.

The most iconic series of the mid-2000s was teen drama The O.C., and the series featured some big-name celebrity guest stars who hadn't achieved monumental fame yet, including Chris Pratt. Introducing a classic fish-out-of-water premise, The O.C. followed Ryan Atwood (Ben McKenzie) as he was transported from a life of domestic abuse and poverty and ushered into the affluent community of Newport Beach, California. Ryan was taken in by his public defender, Sandy (Peter Gallagher), and Sandy's wife, Kristen (Kelly Rowan). Along with Cohen's son Seth (Adrien Brody) and newfound love interest Marissa (Mischa Barton), Ryan went through high school and eventually college.

One of the few exceptions among countless mid-2000s shows, The O.C. still holds up almost 20 years later, thanks to its strong character arcs, comedic leanings in the face of dramatic storylines, and important lessons throughout. While The O.C. arguably veered into the territory of after-school-special tropes, its drama was one of its most charming aspects. The show was phenomenally successful during its four-season run. This popularity inevitably brought some major celebrity cameos into the mix, but The O.C. also cast some actors who weren't well-known at the time in minor roles. Several went on to become huge stars.

11 Chris Pratt

Before his Guardians of the Galaxy and Parks & Rec fame, actor Chris Pratt had an arc on The O.C. season 4 as college activist Winchester "Ché" Cook. Ché met Summer (Rachel Bilson) while the two were attending Brown University, and she quickly conformed to his ideals, leading to a spot of trouble. Something of a secondary antagonist, Ché put the blame on summer and got her suspended after the pair broke into a science lab together. While Pratt's Ché attempted to make amends, the discovery that he was actually a trust fund kid posing as a hippie soured Summer's opinion of him.

10 Olivia Wilde

Olivia Wilde is normally associated with her best movies, but she's another big celebrity who found fame after appearing in a small arc on The O.C. Wilde played Alex Kelly, the manager of the Bait Shop in The O.C. season 2, and she became the series' bad girl. Alex was expelled from both the Catholic school Mater Dei and Newport Union High School prior to meeting Seth and Marissa. Alex was bisexual, and initially dated Seth before moving on to Marissa. While the series handled this LGBTQ+ storyline about as gracefully as any other mid-2000s show, it was still considered somewhat groundbreaking for its time.

9 Amber Heard

Now known as Aquaman's Mera, actress Amber Heard also appeared on The O.C. in a bit role. Her character was never given a name, referred to only as "Salesgirl" throughout The O.C. season 2, episode 15, "The Mallpisode." The installment found the main players in The O.C. cast stuck in the mall overnight. They chose to spend their time going over the various states of their love lives. Heard didn't have a ton of lines or screen time in her blink-and-it's-gone cameo, but she played the snide and apathetic Cali girl with ease.

8 Colin Hanks

Tom Hanks's son, Colin Hanks, is most well-known for portraying Preston in King Kong and Shaun in Orange County. It was this mid-2000s notoriety that earned him a small cameo on The O.C.. Hanks appeared early in the show as Grady Bridges, a fictional soap opera star who made a at Summer during an exclusive L.A. party. Hanks appeared in The O.C. season 1, episode 22, "The L.A.", which also included a few other celebrities, as the gang inadvertently attended a Hollywood party while trying to find Hailey (Amanda Righetti).

7 George Lucas

Star Wars and Indiana Jones creator George Lucas has made many cameos in movies and TV over the years, The O.C. included. Lucas played himself in The O.C. season 2, episode 23, "The O.Sea." While the auteur's main plot thread saw him meeting with Reed Carlson (Marguerite Moreau) to talk about turning Atomic County into a movie, the real highlight was getting to see Seth meet one of his heroes. In the meantime, Lucas inadvertently convinced Seth that he shouldn't miss his prom, leading Seth to call Zach (Michael Cassidy) to finish off the meeting and convene at the dance with Summer.

6 Jeffrey Dean Morgan

Jeffrey Dean Morgan has made a name for himself playing complex villains and antiheroes like Negan from The Walking Dead and Dead City. The actor started this trend early, appearing as Joe Zukowski in The O.C. season 2, episode 10, "The Accomplice." Joe was in prison for the entire episode, but it was revealed that he's a friend of Sandy Cohen's, prompting Sandy to pay him a visit. Their relationship came off as contentious at best, with Joe attempting to get an appeal on his manslaughter case. Joe had crucial information about Rebecca, and he shocked Sandy to the core by claiming she was dead.

5 Max Greenfield

Before playing the funniest New Girl character Schmidt, actor Max Greenfield occupied a guest role on The O.C. Occasionally, The O.C. used flashbacks to move the narrative forward and provide crucial information. In one such flashback, Greenfield got the honor of playing Sandy Cohen during his college years. Greenfield did this in The O.C. season 4, episode 13, "The Case of the Franks," which revealed how Sandy and Kirsten met. It was a sweet scene that gave audiences a glimpse into the earliest stages of their relationship. Greenfield managed to capture Gallagher's character and mannerisms perfectly.

4 Bella Thorne

Transitioning from Disney Channel star to movie star, actress Bella Thorne is particularly well-known among Gen Z viewers. She famously appeared in The Babysitter franchise. However, one of her very first acting credits was in The O.C. where she played young Taylor Townsend (Autumn Reeser). While she didn't really look anything like Reeser, Thorne appeared as her character in The O.C. season 4, episode 13, "The Case of the Franks." She showed up during a flashback, detaling how young Taylor and Summer met. Taylor gave Summer her original poem to read in class in exchange for an invite to Summer's birthday party. The rest was back-stabbing frenemy history.

3 Steve-O

Jackass was at the peak of its popularity in the mid-2000s, as evidenced by Steve-O's cameo in The O.C. Steve-O accrued some scary injuries thanks to Jackass, but his appearance in the teen drama didn't include any major stunts. Simply named "First Marine," Steve-O showed up in The O.C. season 4, episode 2, "The Gringos." He played a completely unhinged marine who coerces Seth into taking a ton of shots while in Mexico. It was the perfect role for Steve-O to take on, and he kept the laughs coming whenever he was on-screen.

2 Paris Hilton

The it-girl of the mid-2000s was Paris Hilton, so The O.C. would have been remiss not to include her in at least one installment. Hilton appeared in the same episode as Hanks, popping up at the Hollywood party in The O.C. season 1, episode 22, "The L.A." Her character was a socialite named Kate, and she managed to steal a kiss from Seth. She also revealed that she's a graduate student at UCLA, but she asked Seth to keep it a secret, as it would ruin her reputation — a fun jab at the persona she took on for The Simple Life.