* ActorAllusion: At Kaitlin's school, Marissa pretends to be an exchange student from London. Mischa Barton was born in London to British parents. OohMeAccentsSlipping also applies and is lampshaded.
* CastingGag: Tate Donovan plays Jimmy Cooper (Father to Marissa & Kaitlin) and voiced the title character in Disney's ''[[Disney/{{Hercules}} Hercules]]''. When the decision was made to finally introduce Frank Atwood (Ryan's father) in season 4, Kevin Sorbo got the role; Sorbo having played the title character in the unrelated ''Series/HerculesTheLegendaryJourneys''.
* CreatorBreakdown - Josh Schwartz was jaded by pressure from some fans and ExecutiveMeddling and seemingly zoned out during Season 3.
* DawsonCasting:
** Benjamin Mackenzie, Adam Brody, Rachel Bilson & Autumn Reeser were all in their early to mid twenties playing teenagers. Lampshaded in "The L.A."
-->'''Ryan''' (speaking of the star from the ShowWithinAShow): How does that guy play high school?\\
'''Seth''': It's ''Hollywood'', man.
** Averted with the Coopers. Mischa Barton was 17 playing 16 and Willa Holland was 14 playing 14.
* {{Defictionalization}}: Before the series, "OC" was sometimes used in print as shorthand for "Orange County," but very rarely in speech, and never prefixed with a "the." Many Orange County residents scoffed at the show's title, but over the years, some of them really do refer to the region "the OC" without irony.
* DuelingShows: With OneTreeHill. The latter lasted longer, but The OC is usually thought to be the better of the two.
* ExecutiveMeddling - Resulted in the end of the Marissa/Alex lesbian relationship. Also, apparently a big factor for the quality decline in Season 3, as Fox wanted something 'promotable' to happen every week. The writers once got a note that said, "This is Fox, not Fox Searchlight".
* HeyItsThatGuy
** [[http://www.imdb.com/name/nm0828177/ Steve-O]] as an insane Marine Seth meets and drinks with in Mexico (4x02)
** [[{{House}} Thirteen]] plays Seth and Marissa's ex-girlfriend and her ex-girlfriend was [[{{Entourage}} Sloan]].
** [[{{Twilight}} Rosalie Hale]] plays one of Ryan's girlfriends and James plays the antagonist of season 3 [[spoiler: who kills Marissa]].
*** Plus Jasper romanced Kaitlin.
** Apparently when Taylor was a kid she looked like a younger version of [[ShakeItUp CeCe]].
*** And when Sandy was in college he looked like [[NewGirl Schmidt]].
** LucyHale plays Kaitlin's roommate, whose father created The Valley.
** [[Series/PrettyLittleLiars Hanna Marin]] as the AlphaBitch of Kaitlin's class and one of the girls that she bosses around is Mona Vanderwal.
** [[Series/TheVampireDiaries Vicki Donovan]] is one of Marissa's friends at Newport Union.
*** And Stefan Salvatore shot Luke.
** [[TheSecretLifeOfTheAmericanTeenager Amy Juergens]] was Marissa's sister in Season 1.
** Che wound up playing [[Film/{{Moneyball}} First base for the Oakland Athetics]].
** Julie Cooper used to run a brothel on a border planet and slept with [[{{Firefly}} Malcolm Reynolds]].
** And of course [[Series/HerculesTheLegendaryJourneys Hercules]] as Ryan's father.
*** Funny thing, [[{{Disney/Hercules}} Disney's Hercules]] is Marissa's father.
** Ryan later made up for his criminal past by becoming a [[Series/{{Southland}} Police officer]]. When that didn't work, he became [[ComicBook/BatmanYearOne Batman instead]].
** [[HartOfDixie Wade]] was on the water polo team. Why does he have cornrows.
** Volchok cheated on Marissa with [[BeverlyHills90210 Naomi Clark]].
** [[GoodLuckCharlie Bob Duncan]] is Harbor's soccer coach.
* McLeaned: [[spoiler:Marissa Cooper]] was killed off at the end of season 3, as the actor wanted off the show.
* TheOtherDarrin: Kaitlin Cooper, Trey Atwood, and Theresa's mother.
* PlayingGertrude: Amanda Righetti was 20 playing 25 year old Hailey Nichol. This also resulted in her being younger than Adam Brody, who was playing her teenaged nephew.
* RomanceOnTheSet: Adam Brody and Rachel Bilson were engaged in real life.
* WhatCouldHaveBeen:
** Kaitlin was reintroduced in season 3 with a view to creating a spin-off following Kaitlin & her friends at boarding school. This was then retooled into keeping Kaitlin as a main cast member in the fourth season so they could keep the high school drama aspect of the show after the original group had graduated.
** The writers tried to get Trey to return in Season 4 to finish his story arc.
** In the same season, AlGore was supposed to be Summer's GEORGE recruiter, but had scheduling differences.