Ryan learns to appreciate his new life in Newport once his mom, Dawn, visits and makes a scene at a casino night event.

Kirsten's dad Caleb features in plenty of big episodes, but the one where he's first introduced needs more love. In this one, Caleb's dating a 24-year-old model, who is only dating him for his money, and soon sets her sights on Ryan.

This episode is hilarious and vastly underrated. The gang becomes obsessed with Rooney, and Oliver uses this as his moment to shine, giving them backstage access to their show at The Bait Shop.

This is the episode where the gang goes to Palm Springs with Oliver, and Ryan tries to warn Marissa to no avail. And then there's the awkwardness of Summer hanging out with new couple Seth and Anna, while still having feelings for him. It's a great one for shouting at your TV.

Other trip episodes are better remembered, but this one includes just as much drama, from the star of Summer's favorite show trying to hook up with her, to Paris Hilton flirting with Seth. And then, of course, there's Kirsten's sister Hailey stripping at the party.

The Nana is spoken of as an antagonist at the beginning of the episode, but by the end it's revealed that she's actually kind and sensitive, and willing to make up for her mistakes after she's diagnosed with cancer.

The Mexico trip is known for being the wildest one of the first season, but we should really talk about how Seth ended up accidentally making out with an escort and then has to find a way to pay her while in Las Vegas.

So many things start thanks to this episode, where Seth gets a job at The Bait Shop and Ryan meets Lindsay.

This episode is one of the best of Season 2, with Seth and Ryan going on extremely awkward double dates with Lindsay and Alex and later realizing that they should be with the other person.

It's not The O.C. without messiness, and this underrated episode is full of it. There's Ryan and Lindsay hiding their relationship after they find out that she's Kirsten's half sister, making her Ryan's adoptive aunt. There's Marissa confronting her parents with a huge fight. Plus, who can forget drunk Seth?

Lindsay tries to get closer to Caleb with Ryan's encouragement, Marissa and Alex's friendship begins to turn into something more, and Seth writes his comic book with Zach.

Sometimes, when the gang gets in trouble, it's a total accident. In this episode, the core four get stuck inside a mall and decide to make the best of it. Until the cops arrive, that is.

There are two things that make this episode great: Julie freaking out over her porn movie being used to blackmail her and Zach making up an Italian girlfriend so Summer won't know he's heartbroken after she left him for Seth. Plus, this is when Ryan's brother Trey comes to town.

Seth and Summer had their ups and downs, and this episode includes one of the most hilarious ways Seth screws up. His trip to visit Nana has some unexpected results, i.e. Seth licking whipped cream off of a girl on live T.V.

Of course you remember the "mmm whatcha say" moment where Marissa shoots Trey. But in this episode, she copes with the aftermath, and Kirsten deals with a rehab friend trying to con her.

This is the episode of the disastrous summer carnival, where Ryan and Marissa try to recreate the moment from the first season where they kissed on the ferris wheel. But it's cut short when Dean Hess expels them.

Sadie might not have been Ryan's best love interest, but this episode marks the beginning of their romance, where Ryan travels with her to find Johnny's dad after his death. And this is also the episode where Marissa begins her tumultuous romance with Volchok, who ends up killing her.

This episode shows how much the Cohens have become Ryan's real family, when he meets up with his mom with the intention of inviting her to his graduation.

Even though Seth's trip to Brown is a bust, he ends up meeting up with Anna, who he hadn't seen since she moved in the first season.

The prom episode is overshadowed by other school dance storylines, but this one isn't exactly boring. Volchok cheats on Marissa, and Seth comes up with a plan to win Summer back.

Underrated, but so important. In this one, Summer visits a therapist for the first time to process her grief over Marissa's death, opening up a conversation about the importance of mental health.

This episode is the beginning of a lot of big changes in the fourth season. Summer gets kicked out of Brown, and Taylor does everything in her power to entice, which kicks off their surprising love story.

It's fair to say that all of the fourth season is underrated, but this one really stands out. It's The O.C.'s spin on The Christmas Carol, basically proves that Taylor and Ryan are the show's true OTP.

This episode was ahead of its time, with Taylor championing sex positivity after her ex-husband publishes a novel based on their steamy sex life.

Are we just not going to talk about how Che thinks Seth is his soulmate after a dream and subsequently tries to seduce him?

The O.C. is packed with hidden gems, so don't skip these episodes during your next rewatch.