The Cast Of 'The O.C.' In The First Episode Vs. The Last Episode Shows How Much Newport's Finest Changed In Four Seasons

By the end, Ryan had ditched his bad boy past and become an accomplished architect, even trading in his signature white tank and leather jacket for a button down and slacks.

Marissa Cooper was first introduced as the beautiful but troubled girl next door.

As fans well know, Marissa was tragically killed in a car accident at the end of Season 3 and never made it to The O.C.'s series finale. But in a later episode, "The Chrismukk-huh?" it's revealed that if it weren't for Ryan, she would have died much earlier, after her overdose in Season 1. Having Ryan in her life allowed her find love before her death.

When viewers first meet Seth, he's a comic book-loving outcast with a major (but unrequited) crush on Summer Roberts.

After a tumultuous but endearing courtship, Seth marries Summer during the Season 4 finale and lands a best friend — Ryan — along the way.

Summer initially came off as shallow, self-involved, and a little bit of an airhead.

Summer eventually learns to stop focusing so much of her energy on status and popularity, finds her passion fighting for animal rights, and marries Seth.

For much of The O.C., Sandy is portrayed as a devoted husband and father. He spends his days sticking up for the underdog as a public defender and frequently acts as a moral guidepost for Seth and Ryan.

Sandy loses himself a little bit along the way, but eventually goes back to his roots and becomes a law professor at UC Berkeley, where he and Kirsten first met and began raising Seth.

At the start of The O.C., Kirsten is a wildly successful but perhaps over-dedicated real estate mogul struggling to balance her work and home lives.

After overcoming her alcoholism in Season 3, Kirsten rededicates herself to her family, has another baby — Sophia — with Sandy, and moves back with him to Berkeley to raise her.

At the start of The O.C., Julie Cooper is a materialistic and domineering mother so concerned with climbing the social hierarchy that she fails to notice her daughter's increasingly out of control behavior.

The show eventually peels back her callous exterior to reveal a caring, tenacious woman. She goes back to school to get a degree, and decides to remain single rather than marry Bullit or Frank Atwood. Fans last see her graduating from college while her family — Cooper, her son with Frank, included — cheering her on from the audience.

Jimmy Cooper is a doting father and husband who gets in way over his head when he starts embezzling to provide for his family’s lavish lifestyle.

Despite a clear love for his family, Jimmy never seems to escape his desperate tendencies, and ultimately skips town to get away from a vengeful loan shark. He ends up working on a cruise ship, and is last seen during flashbacks in Season 3.

First played by Shailene Woodley, Kaitlin Cooper is but a child when viewers first see her.

Willa Holland takes the reins as Kaitlin when she returns from boarding school in Season 3. She's initially quite a troublemaker, but later grows into a strong, supportive daughter that stands by Julie throughout hard times.

Luke is introduced as Marissa’s cheating, water polo-playing boyfriend.

After many wrong turns — including a sordid affair with Marissa’s mother — Luke salvages his relationship with the core four and moves to Portland to live with his father. He’s last seen in the first episode of Season 2, when Ryan goes to Portland to convince Seth to come back to Newport.

Caleb first appears as Kirsten's hardened magnate father.

He seems to soften over the years — in part due to the arrival of his illegitimate child, Lindsay — and later marries Julie. In Season 2, however, he dies of a fatal heart attack, and it's revealed he was actually in severe financial debt.

Hailey Nichol makes her debut as Kirsten's hard-partying sister in Season 1 episode, "The Countdown."

After a whirlwind romance with Jimmy, Hailey leaves Newport in Season 2 when she gets a job in the Tokyo fashion scene. She returns several episodes later for Caleb's funeral, having apparently left her wild ways in the past to become a driven career woman.

Fans first meet Taylor as an uppity, type A honor student.

As the show goes on, she grows ever entwined with the lives of the core four, becoming best friends with Summer and sparking up an on-again, off-again romance with Ryan. Taylor ultimately moves back to Paris and they go their separate ways, but she exchanges longing glances with Ryan during Seth and Summer's finale wedding that seem to suggest their relationship isn't completely over.

Ryan lands in jail when his older brother, Trey, convinces him to steal a car in the pilot episode.

After being released from prison in Season 2, Trey tries to start fresh but falls back on his criminal past, and a violent fight in his apartment leads to Marissa shooting Trey. He survives, but realizes it's best if he leave town and takes a bus to Vegas.

Ryan's ex-con father, Frank, comes barreling back into his life in Season 4, apparently wanting to make amends for his wrongdoings.

Frank later starts a secret affair with Julie and falls in love. They have a son together, Cooper, but she chooses to stay single. He's seen in the series finale at Julie's college graduation.

Gordon, a Texas oil tycoon, shows up in Season 4 and does his best to woo Julie.

Bullit develops a close relationship with Kaitlin, and proposes to a pregnant Julie even though he realizes her heart is with Frank. She doesn't pick either of them in the end, but he remains a close family friend, and is seen cheering Julie on at her college graduation in the series finale.