Abusive Parents: Frank Atwood and many of Ryan's mother's boyfriends. Ryan gets hit in the face by one five minutes into the Pilot.
Badass Bookworm: Ryan is definitely a badass, and is later shown to get very good marks despite his standoffish attitude towards academics.
Bad Liar: Being honest by nature, Ryan is bad at lying.
Beware the Quiet Ones: He's stoic, taciturn and usually reserved and level-headed, but has a violent side due to his rough upbringing. He gets better, though.
Book Dumb: His school grades are not necessarily bad, but as smart as he is, he could do better. Subverted later on as, while his attitude remains somewhat reluctant, he's revealed to get very good grades while living in Newport.
Brilliant, but Lazy: He's very intelligent and easily gets good marks, but it seems doesn't care too much about school most of the time. Though it's disillusionment more than laziness.
Broken Bird: A male teen example, who has become stoic and melancholic because of his past.
Byronic Hero: Dark and Troubled Past? Check. Intelligent? Check. Physically attractive? Check. A brooding, troubled and introspective loner? Oh yes. He has many traits, still he's by no means morally ambiguous, being actually a very good natured and kind-hearted Hero with Bad Publicity.
Character Development: He becomes less short-tempered as the series progresses; still, he can't tolerate injustice.
Chick Magnet: Attracts the attention of Summer, Marissa, Gabrielle, Theresa, Lindsay, Sadie, Taylor, and his one-night stand Chloe.
Chronic Hero Syndrome: Lampshaded at separate times by different characters in Season 1, 2, 3, and 4. One episode in Season 3 had Kirsten helping Ryan to figure out he doesn't need to help every Damsel in Distress anymore. One episode in Season 4 had Sandy helping Ryan to figure out he needs to help every Damsel in Distress because it's "his thing" and he "shouldn't turn his back on that".
Genius Bruiser: He's very tough and he has been described as highly intelligent.
Good Is Not Nice: Mostly subverted, as he really is a nice person, but his exterior would say otherwise. He is a good person at heart and always does the right thing but he isn't exactly affable at first.
Bitch in Sheep's Clothing: Seth arguably started as one or Took a Level in Jerkass; while he comes across as an awkward, friendly and adorable geek, he actually has a big ego, talking very much about himself most of the time, definitely doesn't like it when others change the subject (to the point he gets mad and nervous), and can be a cowardly Consummate Liar and somewhat petty, especially when things don't go his way. This is still downplayed, as he's not that nasty and he still is a genuinely good person, despite his self-centeredness.
Bunny-Ears Lawyer: Socially awkward and sometimes goofy, but this certainly doesn't make him any less smart.
Classical Anti-Hero: Seth is not exactly flawless: he's pretty insecure, self-absorbed, kind of an apathetic coward, socially awkward and sort of a loser. He would be a loner if it wasn't for Ryan and for Summer, respectively his best friend and girlfriend, who understand he's ultimately a good natured guy with a kind heart (although with a bit of a bratty Jerk with a Heart of Gold streak).
Cloudcuckoolander: He kinda lives in his own world; justified as he's a geek who loves comic books living in a place where most young people are jocks and party girls.
Consummate Liar: Seth can be this at times. Especially when situations don't go his way and he has to save his own skin, to the expense of others. Summer obviously can't stand his insincerity; he gets better, though.
Cool Loser: Seth is clearly an attractive, talented, funny and ridiculously rich young man, yet he couldn't get a date for most of his life, despite living in a town full of golddiggers, and was constantly being beaten up by jocks. He apparently had no friends at all prior the arrival of Ryan. It's implied that Seth would probably be popular if he lived anywhere besides Orange County. This is particularly obvious when he briefly moves to Portland, and apparently has no trouble making friends. It's just that he's surrounded by people who are pompous and shallow.
Deadpan Snarker: Incarnate. His trademark sarcasm is a notable aspect of his personality, and inherited from his father. However, he doesn't really want to irritate others, despite being sometimes mistaken for being ill-mannered.
Ditzy Genius: He's clearly very intelligent, with a quick wit, and a good logical thinker, but socially speaking, he's pretty naive and awkward. This is justified due to the frivolous and materialistic society that surrounds him, as he has no problems becoming friends with people who aren't shallow and brainless (and, of course, said people are even more likely to befriend him if they're kinda quirky).
Endearingly Dorky: A socially awkward, self-proclaimed geek and comic book lover with a great sense of humor. He's shown to be a Chick Magnet, being able to attract popular girls like Summer, tough girls like Alex, and girls who are as nerdy as him like Anna and Taylor.
Fanboy: Seth is a nerd and loves comic books, anime, and video games.
Foil: To Ryan. He's outgoing, quite impractical, carefree and witty, while Ryan is brooding and Street Smart. Ryan had Abusive Parents (at least his father and the stepfathers he had), Seth has Good Parents. Ryan is a naturally selfless guy who comes from a poor family, while Seth is rich, spoiled and used to be pretty selfish most of the time, although he gets better.
Four-Temperament Ensemble: A blend of Sanguine and Phlegmatic. He's quite outgoing, friendly and cheerful, but not bubbly and energetic as Summer.
Hollywood Nerd: He is supposed to be an unattractive nerd due to his social awkwardness and huge interest in comic books and science fiction. This doesn't really work since he's also sweet, funny, and played by the attractive Adam Brody.
It's All About Me: He can be incredibly self-absorbed and gets mad when other people change the subject.
Jerk with a Heart of Gold: Downplayed. He may be self-absorbed, can be a liar and slightly petty at times, but otherwise he's a genuinely Nice Guy, who is ultimately not as mischievous as he looks, and to be fair he's just a bit cowardly and insecure rather than a true jerk. He loves Summer more than anything, and most of his selfless and sweet moments occur when he's with her, or when the situation involves her. When he wasn't accepted to his preferred university, and she refused to go without him, he broke up with her and told her didn't love her anymore just so she would go. And he clearly did still love her. And how can we forget all the times where he looked after her and his mother while they were drunk? Plus, as far as he's concern, Ryan is his best friend and brother and will do whatever is in Ryan's best interests (even when Ryan doesn't want it).
Mushroom Samba: In Season 4, Seth takes hallucinogenic berries in an attempt to "heal his animus". He then has a vision of walking through a tripped-out version of the Cohen house until he walks into his room. His room now has a pool in it, where Seth's spirit animal, an otter, flops out of the pool. Seth begins to talk to him. When the vision ends, Seth has been renewed spiritually by 'saving his spirit animal', and is thus ready to love again.
Nerds Are Sexy: Played by the handsome Adam Brody and has quite a few girls attracted to him on the show.
The Alcoholic: In season 2, she struggles with alcohol and depression. She already drank quite a lot in season 1, and it was at that moment that Ryan started to be very worried about her.
All Girls Want Bad Boys: Besides Ryan, there's also Volchok in season 3. She is aware that he is "bad" by most people's standards, but continues to engage in a relationship with him until he cheats on her.
Anyone Can Die: Especially surprising considering there was no real warning for it in the press, and the character dies on the way to a bus trip.
Attention Whore: Craving attention from her family through her substance abuse and questionable relationships.
Broken Bird: Starting off as a privileged do-gooder whose family falls apart, and is then forced to deal with her conniving mother, negligent father, controlling stepfather, and basically everyone around her ignoring her rapidly declinging mental health. She's also almost raped by her boyfriend's brother and is then forced to shoot said brother to save Ryan, which sees her kicked out of her school and forced to move away from her friends and boyfriend. And then there's everything else she goes through in Season 3, including watching a friend die, Ryan breaking up with her and falling into a bordeline-abusive relationship.
Byronic Heroine: Even more than Ryan, as she's similar personality wise, but is by far more self-destructive than him. And this very troubled and conflicted girl dies in the end.
Her family went bankrupt thanks to her father and she lost her popularity due to the revelation that her father was stealing from his clients (most of whom are parents of her friends), finally sealing her fate when she overdoses in Tijuana in the first season.
In season 3, Marissa is once again broken (despite having been rich again, thanks to her mother marrying Caleb in season 2), due to her stepfather's secret bankruptcy, and she's expelled from the private high school and begins attending public school due to Trey's shooting.
Four-Temperament Ensemble: Like Ryan, a Melancholic with shades of Choleric; she's troubled and had an impulsive streak, though unlike Ryan she's also self-destructive and addicted to alcohol (and briefly drugs, before her death).
Horrible Judge of Character: In the Oliver story-line of Season 3. Her later dalliance with Volchok doesn't count because she is fully aware he is bad for her.
Ms. Fanservice: Often wears revealing clothes, has some bikini scenes, and especially her scene where she wears a naughty Bare Your Midriffschoolgirl outfit (to help her sister, tricking a boy making him believe she was a stripper) is very fanservicey.
Ms. Vice Girl: Marissa is a good person but has several bad habits, especially drinking. This is due to her emotional instability.
Opposites Attract: Ryan/Marissa (wrong side of the tracks + (seemingly) perfect debutante).
Rebellious Princess: A privileged rich girl with a history of substance abuse and rebellious behavior.
Brilliant, but Lazy: It's discovered in season 3 that she has higher SAT scores than Seth, and Dr. Kim notes to Summer that every few years Harbor has a student with high aptitude and potential that remains untapped as they spent their time gossiping and shopping rather than studying.
Character Development: In the first episode she was more like Holly Fischer, going as far as to dump the drunk Marissa on her front door and flirt with Luke... Later, the shallow, somewhat bitchy party girl becomes a Nice Girl who's a loyal friend and a bit of an airhead.
Daddy's Girl: Summer and her dad really love each other and have a very good relationship. She always describes her dad as her best friend.
Divergent Character Evolution: At the beginning, Summer and Holly were distingushable only by hair colour, both being vapid, self absorbed party girls who happened to be friends of Marissa. Summer grew more likeable, became a main character and hooked up with Seth. Holly had an affair with Marissa's boyfriend and was quickly Put on a Bus after the cheating was revealed.
Dude Magnet: Just watch all of boys waiting to kiss her during "The Kissing Booth" event in 1x20.
Four-Temperament Ensemble: Sanguine. She's very energetic, has a bright and optimistic outlook on life, and is ultimately a very sweet and kind girl. She is also definitely emotional and can act on impulse.
Jerkass Façade: It's shown pretty soon that she isn't by any means vain and materialistic as you may think at the beginning of the series.
Jerk with a Heart of Gold: At the beginning, she was a bit bitchy at times; later she turns out to be a Nice Girl. She has a genuinely good heart, is a good friend to Marissa and Ryan and a loving girlfriend to Seth.
Last-Name Basis: She persists in calling Seth by his last name, Cohen, even after they're in a relationship.
Academic Alpha Bitch: She starts out as an extremely competitive power-grabbing overachiever who antagonizes Summer. In early season 3 she also acts like a stereotypical Alpha Bitch except she isn't popular at all.
Cloudcuckoolander: She's quite eccentric, has a vivid imagination, and is definitely talkative.
Cool Loser: A stunning, whip smart, witty young lady who is so unpopular she is reduced to following around Seth (and Summer) for want of a friend. Justified because her attitude can be annoying sometimes.
I Have No Son!: Gets kicked out of her house by her mother and told she isn't welcome there anymore after her marriage is revealed. Given how her home life was characterized by intense verbal and emotional abuse, it was probably the nicest thing she did for Taylor, albeit unintentionally.
I Just Want to Be Loved: She will relentlessly pursue anyone who shows her even the slightest amount of affection due to growing up with a heartless, emotionally abusive mother. She at least seems aware of it though.
Remember the New Guy?: She first appears at the start of the third season, but apparently had been going to the same school as the main characters for the entire time. Indeed a later flashback reveals she had been friends (or at least on name terms) with Summer since they had been in elementary school.
The Alcoholic: In season 2, when her marriage with Sandy begins to deteriorate.
Blonde Republican Sex Kitten: At one point in the show Sandy mentions to another character that Kirsten is a political conservative. There are also a few points in the show where Kirsten criticizes Sandy's "hippie parenting."
Broken Bird: Probably the most traditional version, born into a wealthy, emotionally-detached family with a cheating, power-hungry father and an alcoholic mother who dies long before the series begins. She channels this trauma into becoming a "Well Done, Daughter!" Girl and eventual Lady Drunk.
Deadpan Snarker: Not to her son and husband's extent, but she's still pretty sarcastic.
Defrosting Ice Queen: Before Ryan joined the family and caused her to soften, although she was rather disillusioned and strict than actually cold. Lampshaded in a touching scene in the fourth season premiere, "The Avengers", when Seth puts together a comic book illustrating the Cohens' lives before he joined the family.
Kirsten: The ice queen was surrounded by an impenetrable force field and her silver cell phone was her only link to the outside world.
Good Parents: Like her husband, she's a good parental figure to both Seth and later to Ryan.
Hair of Gold, Heart of Gold: She may be somewhat distrustful and was a bit distant towards Ryan, but she's undoubtedly kind-hearted and one of the most morally upstanding individuals in the series. And she's a blonde.
Lady Drunk: Played for laughs in the first season but builds to drama by the end of the second.
Anti-Villain: Julie isn't outright evil, but definitely morally ambiguous. She's utterly selfish, opportunistic and greedy, but has redeeming qualities. On a D&D chart, she'd be Chaotic Neutral.
Chronic Villainy: She switches between trying to be a good mom and being a gold-digging manipulative slut schizophrenically throughout the series.
Defrosting Ice Queen: Although by far more bitchy than icy, Julie Cooper very gradually becomes more sympathetic as the show goes on. By the final season, she had shed much of the bitchiness that defined her in the show's first few seasons.
Everyone Has Standards: She may not be the most morally upstanding character in the series, but at least when con artist Charlotte proposes her, she doesn't betray Kirsten, as she considers her as a good friend and she doesn't want to take advantage of her good heart.
Evil Redhead: Although evil is a stretch, she's definitely one of the most devious, selfish characters. She's also the main antagonist in early seasons.
Femme Fatale: She uses her beauty to exploit wealthy and influential men... And even to seduce attractive boys such as Luke.
Good Parents: He's certainly a better parent to Marissa than Julie is.
Jerk with a Heart of Gold: Irresponsible and immature, but he loves his daughter Marissa. While he committed crimes because of his personal problems, he's still a good man deep down.
Put on a Bus: Despite being important enough that he received an And Starring in the opening titles. With his relationship with Hailey ending early in the second season,he kinda just floated around (Literally, he was living on a boat) for the first half of the season as the character had run his course. The writers figured this out towards the middle of the season, so he was written out of with the explanation he was worried, since he was restarting his relationship with Julie, that he was just repeating the cycle that cost him his marriage & reputation so he was going to move to Maui.
Jerk with a Heart of Gold: Kaitlin may be bratty and mischievous, but she has a big heart, and though she doesn't always say it the right way, she cares about people. She once threw a party solely so two girls that she barely knew could attend because they hadn't been invited to the Alpha Bitch's party.
Troubled, but Cute: Female example. Has a Dark and Troubled Past, her parents never were on her side, she dropped out of school and was forced to work. Still, she's definitely attractive and despite her tough image and brash attitude she's quite kind.
Love Hurts: His feelings for Marissa are unrequited, and Johnny is very sad about it, until his death.
Love Makes You Crazy: Because of his unrequited love for Marissa, he drinks too much and falls off a cliff before Ryan could save him. Sadly, when the doctors try to save him, he dies in the hospital, and his mother calls Ryan to tell him he tragically didn't manage to survive.
Nice Guy: He's kind and gentle, although troubled.
Troubled, but Cute: A guy with a Dark and Troubled Past who is pretty similar to Ryan. Johnny is a good person, but he had to beat the crap out of his father because of how he treated his mother, and now he's lonely and depressed.
The Bully: He repeatedly tries to fight Ryan because he wants a rematch after the latter punches him in the face.
The Corrupter: When he blackmails Ryan initially to participate in a robbery, along with car theft, to help him escape Newport.
Delinquents: A bully and a thief who also blackmails Ryan into a crime.
Hidden Heart of Gold: Although "gold" is a stretch. This is seen mostly in season 4, but he shows signs of this even in season 3: he was really sad about Johnny's death and deep down, he really cared about his relationship with Marissa, albeit in a dysfunctional way.
Jerk Jock: A jerkass surfer dude. He's rude, amoral and lives the typical bad boy life.
Divergent Character Evolution: Very early on she and Summer were distingushable only by hair colour, both being vapid, self-absorbed party girls. This is actually Lampshaded by the show in the "The Chrismukk-huh?" where see a universe where Summer continued to be friends with Holly rather than going through Character Development. It is not a pretty picture.
Dumb Blonde: In season 4, there are a lot of jokes about her airheadedness ("Who says I can't have a baby and a six pack?").