Summary

• The O.C. featured a cast with significant age differences, with actors in their twenties playing high school students, but they still portrayed their characters well.
• Ben McKenzie, who played Ryan, was 25 years old when the show began, while Mischa Barton, as Marissa, was just 17, making her the youngest member of the main cast.
• One of the adult characters, Sandy, played by Peter Gallagher, was also significantly older than his character.

The O.C. aired from 2003 to 2007 and is one of the staple teen dramas from the aughts, partly thanks to its iconic cast. As the name of the Fox television series suggests, it took place in Orange County (The O.C.) in Southern California and ran for four seasons before the network canceled it. The show's catalyst was when Ryan Atwood, a troubled teenager from a broken home in Chino, moved in with the Cohens, a wealthy family living in an upper-class community in Newport Beach. Ryan and the Cohens, which included Sandy, Kirsten, and Seth, came from different worlds, but they eventually learned how to operate as a unit.

Although the series contained a plethora of side plots and important storylines, the central one (at least, in the beginning) revolved around how Ryan fit in with the rest of the characters. The culture clash between Ryan's upbringing and the Cohens' was a main conflict throughout the series because he was so young and had a rough childhood. Plus, The O.C. had a bit of age diversity in its cast, as some actors played teenagers while others were full-fledged adults (even though they didn't act like it sometimes).

12 Ben McKenzie As Ryan Atwood

Actor Age: 25 / Character Age: 16

Ben McKenzie played Ryan Atwood throughout all four seasons of The O.C., and he undoubtedly had the most character development out of everyone. Ryan was a troubled teenager from the rougher area of Chino. After being kicked out of his home by his mother, Ryan is taken in by Sandy Cohen. Though he is an outsider, he gradually becomes accepted by many in the more affluent community, finding family, friendship, and love in "the O.C."

The actor was almost a full decade older than his character while shooting the first season since McKenzie was 25 years old, and Ryan was 16 years old. It was not uncommon for teenage characters to be played by much older actors in teen dramas, especially in the era, so it is not too surprising to learn the massive age difference between McKenzie and Ryan.

11 Mischa Barton As Marissa Cooper

Actor Age: 17 / Character Age: 16

Marisa Cooper was the privileged high schooler at the beginning of the series who had to struggle with adjusting to a life of less luxury than she was used to. She was also the on-again-off-again love interest for Ryan, finding something alluring in this boy with a darker past.

The struggles of her life, including her parents' divorce led her to an addiction to drinking and drugs though her loved ones stayed by her side. Marissa was killed off in The O.C.'s third season in a car accident. Whereas there was a significant age difference between Ben McKenzie and Ryan, Mischa Barton was much closer to her character's age during the first season of The O.C.

The core four — Ryan, Marissa Cooper, Seth Cohen, and Summer Roberts — were all juniors in high school in the pilot episode, meaning they were 16 years old. Meanwhile, Barton was only one year older than Marissa, making her the youngest main cast member while filming the first episode.

10 Adam Brody As Seth Cohen

Actor Age: 24 / Character Age: 16

Seth Cohen was the only child of Sandy and Kristen Cohen in season 1 of The O.C. Though he was born into the affluent community, he was also seen as something of an outsider as he was "nerdy" and had a lot of disdain for his rich and self-centered peers. This allows him to form a fast connection with Ryan when he arrives. Seth eventually begins to gain confidence, which leads to his relationship with Summer, which gives some of the defining moments in The O.C.

Seth was 16 years old in The O.C. season 1, and his portrayer, Adam Brody, was 24 years old when he was cast in The O.C. Similar to Ben McKenzie, Brody was well into his twenties when he shot his first scenes as Seth in the Fox teen drama television series. But Brody constantly fully leaned into the dorky aspects of his character, which somewhat made him appear younger.

9 Rachel Bilson As Summer Roberts

Actor Age: 22 / Character Age: 16

Rachel Bilson as Summer Roberts was only meant to appear in a few episodes of The O.C., but after the audience fell in love with the character, she became one of the central players in the show. Summer was the best friend of Marissa and was initially seen as stuck-up and meanspirited. However, Bilson quickly turned those qualities into comedic energy, making her one of the funniest characters on the show. Summer and Seth's romance also helped to solidify her place in the series.

As mentioned above, Summer was a junior in high school like the other main characters during season 1, making her 16 years old. However, Bilson was 22 when filming began, so she was six years older than her The O.C. character. Interestingly, Bilson initially wanted to be cast as Marissa in The O.C., but it is a testament to her talents that she was able to bring out so much of the less-developed character of Summer.

8 Peter Gallagher As Sandy Cohen

Actor Age: 48 / Character Age: 30s

Sandy Cohen was the patriarch of the Cohen family in The O.C., and he was the reason why Ryan came to stay with them in the pilot episode. He was a public defender with more liberal views of the world than most of the people in his rich community. He also felt like an outsider in this world in many ways and sees himself in Ryan at times due to his own humble beginnings. Sandy remains a loving father and husband, the kind of role Gallagher always excels in, throughout the series.

His age was never blatantly stated throughout the teen drama series, but it is assumed that he was in his mid-to-late thirties in season 1. Meanwhile, Peter Gallagher, who played Sandy, was 48 years old at the beginning of the show. So, the actors playing teenagers were not the only ones significantly older than their characters.

7 Kelly Rowan As Kirsten Cohen

Actor Age: 38 / Character Age: 30s

Kristen Cohen was the strong matriarch of the Cohen family. While she was initially reluctant to have Ryan live with them, fearing that the troubled teen would be a bad influence on her son, she eventually came to love him like a member of the family.

Kristen was the financial provider for the family, and while she was more entrenched in the uglier side of the community than her husband, she was still a kind and caring mother and wife. Kirsten was the same age as her husband, Sandy, in The O.C., meaning that she was also in her mid-to-late thirties when the Fox television series started.

The matriarch of the Cohen family celebrated her 40th birthday in season 4, so she was likely 38 years old in season 1. While this fact is not confirmed (especially because the timeline of The O.C. can be tricky and have some plot holes), it would make sense because Kelly Rowan, who played Kirsten, was also 38 at the beginning of production.

6 Tate Donovan As Jimmy Cooper

Actor Age: 40 / Character Age: 30s

Jimmy Cooper was one of the characters in The O.C. that brought a lot of drama to the community early on. He was Marissa's father and Julie's husband who was also embezzling money, ruining his reputation in the community and ending his marriage. Jimmy remained a supportive and caring father to his daughters, but he never really got his life together over the course of the series.

Jimmy was the same age as Kirsten in The O.C. since they grew up together and once dated when they were teenagers. So, Jimmy was likely 38 years old in season 1, too, but like the other adult characters in the show, his age was never confirmed in the episodes. Tate Donovan, who portrayed Jimmy in The O.C., was only two years older than the character when the series began.

5 Melinda Clarke As Julie Cooper

Actor Age: 34 / Character Age: 34/35

Julie Cooper is Marissa and Kaitlin's mother who was married to Jimmy only to divorce him when his embezzling was discovered. Julie is presented as a stuck-up and money-driven housewife when she is introduced in the series. She is shallow and self-centered, but there is more to the character revealed throughout the series with her taking charge of her life rather than relying on others to provide for her.

Julie, played by Melinda Clarke, was a little bit younger than the other adult characters in The O.C., but not by too much. Julie got pregnant with Marissa when she was 18 years old, meaning that she gave birth either at 18 or 19. Since Marissa is 16 years old in season 1, that would make her mother either 34 or 35 when the Fox teen drama series began. Unlike many of the other actors, Clarke was around the same age as her character.

4 Alan Dale As Caleb Nichol

Actor Age: 56 / Character Age: 50s

Caleb Nichol is one of the most intimidating characters in the series. He is an important figure in the Newport community as a gruff, unsympathetic, and demanding man of action. He is also Kristen's father with whom he has a strained relationship partially due to the fact that he has never liked Sandy. Later, the relationships on the show get even more entangled as Caleb marries Julie, becoming Marissa's stepfather.

Unlike the other characters in The O.C., it is difficult to gauge Caleb's age, but it might be safe to say that he is in his 50s at the show's beginning. The television series never revealed how old Caleb was throughout the first two seasons. However, given Alan Dale's age during the first season — 56 — Caleb was likely in his fifties. Dale left The O.C. in season 2 when Caleb died from a heart attack.

3 Chris Carmack As Luke Ward

Actor Age: 23 / Character Age: 16

In season 1 of The O.C., Luke Ward is introduced as the villain of the series. He is Marissa's boyfriend who is a popular and aggressive member of the rich kids clique. He quickly butts heads with Ryan, getting into several fights in the pilot episode. After Marissa and Luke break up, he gradually forms a friendship with Ryan and Seth before beginning an affair with Julie Cooper leading to the character leaving the show.

Marissa's boyfriend in The O.C. season 1, Luke Ward, was the same age as the other younger characters in the show. He was 16 years old when the Fox teen drama series premiered, seeing as he was a junior in high school with Marissa, Ryan, Seth, and Summer. Meanwhile, Luke's portrayer, Chris Carmack, turned 23 years old in the middle of filming the first season.

2 Autumn Reeser As Taylor Townsend

Actor Age: 25 / Character Age: 17

Taylor Townsend was introduced in season 3 but became a bigger part of The O.C. in season 4 following Marissa's death. She was a perfectionist student at the high school who served as a villain in the series when she was first introduced.

However, her personality softened in season 4 and she became a more likable character, even beginning a romance with Ryan and taking up the second female lead opposite Rachel Billson's Summer in the final season.

Taylor might not have been introduced until the third season of the show but she was in the same grade as Ryan, Marissa, Seth, and Summer, which would make her around 17 years old in her first episode. In a similar vein to the other younger cast members, Reeser was in her mid-20s when she started filming the television series.

1 Willa Holland As Kaitlin Cooper

Actor Age: 15 / Character Age: 15

Shailene Woodley briefly played Kaitlin Cooper, Marissa's younger sister, in The O.C. season 1, but Willa Holland took over the part in season 3 when it became a more significant role. Season 3 of the series saw Kaitlin returning from boarding school with her being revealed to be a more rebellious character than her early appearances suggested. With her experimenting with drugs and acting out, it seems as though Kaitlin was meant to offer a bit of a replacement for Marissa.

Holland was one of the few actors who was the same age as their character while filming the Fox teen drama. Holland was 15 years old in The O.C. season 3, and so was Kaitlin. Interestingly, Woodley was the same age as Holland and was given the opportunity to re-audition for the role when it was decided to expand on Kaitlin's role but Woodley did not get the part.