!!The original series, or the overall franchise
* ApprovalOfGod:
** Creator/ShannenDoherty claims she had a massive crush on Jason Priestley. As such when fans ask her about the IncestSubtext between their characters, her response is "you better believe it".
** Creator/ChristineElise (Emily Valentine) had nothing but love for the 2017 parody ''90210! The Musical''.
* CastIncest: Shannen Doherty (Brenda) and Jason Priestley (Brandon) [[https://www.gettyimages.at/detail/nachrichtenfoto/shannen-doherty-jason-priestley-during-1991-emmy-nachrichtenfoto/111175733 had a brief fling]].
* CastTheRunnerUp:
** Creator/LukePerry auditioned for the role of Steve Sanders, which eventually went to Creator/IanZiering.
** Creator/GabrielleCarteris (Andrea) auditioned for Brenda, even bringing a childhood photo of herself and her brother as she is a real life twin. The producers thought she would be better for Andrea.
** Tori Spelling auditioned for Kelly Taylor, which went to Creator/JennieGarth.
** Kristin Dattilo, who portrayed one-off character Melissa Coolidge in season 1, was the runner-up for Brenda, having been the last, along with Doherty, to test for the network.
* CreatorBacklash:
** Creator/AaronSpelling stated he didn't enjoy the MonochromeCasting, calling it his one regret about the show.
*** However, the writers have revealed in interviews that they were planning to have Donna date D’Shawn in college, but Aaron Spelling killed the story because D’Shawn was black.
** Creator/JasonPriestley disliked Brandon's holier-than-thou attitude, once calling him a "[[https://youtu.be/U-ru7KPYRSE?si=lVwe1KWk14sUMmlA&t=121 sanctimonious prick]]".
** When [[ThrowItIn Andrea got pregnant]] Carteris revealed in a contemporary interview that she really wished they'd "made [Andrea] an exchange student or something". Whether that was because she thought the teen pregnancy storyline was cliched [[note]]and it did stop most of Andrea's potential CharacterDevelopment in it's tracks; nearly every following storyline revolved around her daughter or her marriage, rather than being an academic high-flyer and driven career woman[[/note]] or she simply didn't want to work long days in the later stages of her pregnancy, she's never detailed.
*** Carteris has stated that she specifically asked for her pregnancy and child to be written into the story, which is why it happened. Writer Larry Mollin stated that the writers “did not want to do [a pregnancy storyline for Andrea]” and that it led to the character being written out of the show.
** Ian Ziering didn’t like how Steve’s storyline about being falsely accused of rape turned out. Namely, he felt that he was given some really good material to work with and did his best to practice and authentically sell them...only for much of these lines and scenes to be edited out later, which caused Ziering to trash his dressing room in frustration.
** It has been stated that by season five, the main actors hated being on set (well, except for Tori Spelling).
** Ditto Jamie Walters (see IAmNotSpock section of this page).
* CreatorsFavorite:
** Creator/AaronSpelling was high on Creator/LukePerry - while the network executives didn't believe the character was needed for the show (Dylan was supposed to be around for only six episodes). As a result Spelling paid Perry's salary out of his own pocket. When audiences responded well to his character, he was made a regular cast member.
** For Creator/DarrenStar, Brenda and Dylan's relationship was a favourite.
** Creator/CharlesRosin became the showrunner in seasons 3-5, after series creator Darren Star left to start ''Series/MelrosePlace''. His favourite characters were Brandon, who served as his AuthorAvatar, and Kelly. This is evident in Kelly's increased storylines from Season 3 onwards, until Shannen Doherty left the show and Kelly became the female lead.
** Co-Showrunner in seasons 6 and 7, and writer for the first 7 seasons, Creator/JessicaKlein's favourite character was Andrea Zuckerman.
** Writer for seasons 4-7 Larry Mollin has stated that the writers room loved Brenda because of Shannen Doherty's talent.
* DawsonCasting: In the extreme, to the point where this trope is often called "90210 Syndrome" outside of this wiki, since the extremeness makes ''Series/DawsonsCreek'' look like they cast age-appropriately.
** The original cast members were Creator/JasonPriestley (21), Creator/ShannenDoherty (19), Creator/JennieGarth (18), Creator/IanZiering (26), Creator/GabrielleCarteris (29), Creator/LukePerry (24, but who honestly looked at least five years older), Creator/BrianAustinGreen (17), Douglas Emerson (16), and Creator/ToriSpelling (17). The latter three were the only (high school-aged) actual teenagers in the cast. Plus, James Eckhouse (35) and Carol Potter (42), who definitely didn't play teenagers.
* DirectedByCastMember: Jason Priestley directed 15 episodes, Creator/JamesEckhouse directed three episodes, Jennie Garth directed two episodes, Creator/LukePerry also directed two episodes, Brian Austin Green directed an episode, Tori Spelling also directed an episode, and Creator/IanZiering also directed an episode.
* DyeHard: In the original series, Donna starts off as a blonde, though in later seasons, dyes her hair brown and auburn colors (at different points).
* ExecutiveMeddling:
** After Brenda lost her virginity to Dylan in the season 1 episode “Spring Dance” and it was portrayed as being the right thing, many parents complained to the network. In turn, Fox had the writers include a pregnancy scare for Brenda, resulting in her break-up with Dylan, at the start of the following season in order to placate these parents and show the consequences of teen sex. Executive producer Charles Rosin was not happy about this decision.
** In an interview given shortly after her Best Actress Oscar win for ''Film/BoysDontCry,'' Creator/HilarySwank (Carly, Steve's season 8 girlfriend) revealed that she had been fired from the show because the producers didn't think that Carly was connecting with the show's audience.
* FakeAmerican: Jason Priestley (Brandon Walsh) and Kathleen Robertson (Clare Arnold) are actually Canadian, but they do a good job of hiding it.
* FakeMixedRace: Inverted. Creator/LindsayPrice is biracial--half-Korean, half-Caucasian (Irish/German)-- but was cast as the Japanese-American Janet Sosa, making this a case of FakeNationality as well.
* HostilityOnTheSet:
** Creator/ShannenDoherty frequently clashed with her co-stars, which led to her getting dropped from the show.
** Creator/CharlesRosin was not copasetic with Doherty and as a result, Brenda's storylines were decreased when he took over running the show. It is also evident in the storylines she did get, eg. nobody supporting her when Dylan and Kelly betrayed her. In Season 4, the characters would never support Brenda or get angry with her when she did nothing wrong, all except Dylan. Especially Brandon and Brenda's bond was left by the wayside as Brandon treated Brenda very badly and didn't stand by her in seasons 3 and 4, but she was never allowed to respond to it.
* IAmNotSpock: Jamie Walters actually hated his role as Ray Pruit, Donna's abusive boyfriend, claiming that the character ruined his potential music career by making people refuse to buy any of his albums or concert tickets on the grounds that they actually thought he was like Ray in real life.
* KeepCirculatingTheTapes: All of the [=DVDs=] are severely edited to remove ALL of the popular music from the show along with the various musical acts that performed in the later half of the series, to the point that several episodes have lengthy scenes cut from the DVD due to the music featured in the scenes not being able to be overdubbed. And while reruns on POP Channel are intact music-wise, they cut the credit scenes to run them in fast forward and use the syndicated version of the various two hour episodes (meaning they are cut into two episodes instead of running as two hours).
* TheOtherDarrin:
** In the pilot, Mrs. Taylor is portrayed by Pamela Galloway rather than Ann Gillespie, who even reprises the role in the sequel. Mrs. Martin is also played by Jordana Capra rather than Katherine Cannon in her first appearance (also with a different name - "Nancy Martin" rather than "Felice Martin").
** Dylan's dad Jack [=McKay=] is portrayed by Terence Ford and Arthur Brooks in two different episodes before Josh Taylor assumed the role in season 2.
** Dylan's sister Erica is portrayed by Noley Thornton for the fourth and fifth seasons before being played by Johna Stewart Boden in season 8.
** Andrea's grandmother Rose is played by Lainie Kazan in season 2, with Bess Meisler taking over the role for her remaining appearances.
* TheOtherMarty: Lyman Ward played Jim Walsh in the pilot. But his scenes were cut and re-shot with James Eckhouse.
* PostScriptSeason: Season 8 was gonna be the last, thus the finale episodes center around the wedding of the show's remaining biggest couple, Brandon and Kelly. However, a very late and unexpected renewal resulted in the storyline changing to the wedding being called off. Priestley and Thiessen were ready to finish the show, which resulted in the odd last two seasons with a lot of replacement characters.
* RealLifeRelative: Tori Spelling was the daughter of producer Creator/AaronSpelling. Additionally, one of Steve Sanders' half-brothers Ryan is portrayed by Randy Spelling (Tori's brother and Aaron's son).
* RecastAsARegular: There are numerous examples of this, despite [[WordOfGod seasons 3-5 showrunner Charles Rosin]] asserting that Aaron Spelling ''hated'' this.
** Creator/DavidGail appears as a bellhop in the Season 1, episode "A Fling In Palm Springs", and returns in Season 4 to play Brenda's love interest, Stuart Carson.
** Gordon Currie plays Brenda and Brandon's paternal cousin Bobby in the Season 2 episode "Leading From The Heart" and returns for a few episodes in Season 6 as Colin's drug dealer; although significance of the former part is bigger, the latter had more appearances.
** Steve's love interest in Season 8 is played by Brandi Andres who had a cameo as an extra in a Season 2 episode.
** The actor who plays Kelly's rapist in seasons 9 and 10 appears in the Season 2 episode "Halloween" as a guy who hits on Kelly.
* RecycledScript: Dylan twice has storylines with him becoming addicted to drugs and suffering a near-fatal overdose (though this could also be a realistic portrayal of an addict's struggle), and Andrea's pregnancy complications are revisited when Janet has the same problem.
* RoleEndingMisdemeanor: Creator/ShannenDoherty was fired after Season 4 for allegedly having too many clashes with her co-stars and being frequently late to the set.
* RomanceOnTheSet:
** Shannen Doherty and Luke Perry had a brief fling early in the show, as mentioned by Doherty on a [[https://open.spotify.com/episode/2yOnLzadocnncaKC29JQRK?si=Ig7N4uhxTn6SfgP8uTmtuA 2024 episode of her podcast]].
** Jason Priestley (Brandon) had a five-year relationship with Christine Elise (Emily Valentine).
** Brian Austin Green (David) had numerous relationships, though the one with Creator/TiffaniThiessen (Valerie) existed before she joined the series and lasted only during Season 5. At the time, Green was angry that Thiessen was hired because he didn't want her making out with the other cast members. He later had a son with Vanessa Marcil (Gina), though they too separated.
* ThoseTwoActors: Cari Shayne and Vanessa Marcil of ''Series/GeneralHospital'' (Karen and Brenda, respectively) both appeared on the show at the same time. Ironically, despite having been rivals who eventually became friends on ''GH'', their characters had little to no interaction here.
* WhatCouldHaveBeen:
** There have been long-running rumors that Aaron Spelling wanted to license the Degrassi franchise (specifically the then-running Series/DegrassiHigh) for an American adaptation, but was denied by Linda Schuyler and Kit Hood, the producers of that show. This allegedly led Spelling to create 90210 instead. The show is sometimes compared to ''Degrassi High'', both positively (for being [=Anvilicious=] in it's earlier seasons) and negatively (due to the lack of DawsonCasting in ''Degrassi High'')
** Creator/DrewBarrymore was the first choice to replace Creator/ShannenDoherty as Brenda, but she opted to focus on her film career instead. Creator/AliciaSilverstone also turned down the role. After briefly considering Creator/AlyssaMilano, Creator/TiffaniThiessen was cast.
** Creator/RobynLively was offered the part of Andrea, but turned it down. She commented in 2022 that she had no regrets, especially as she was dating Creator/JasonPriestley at the time and they broke up at the end of the first season, so she would’ve had to work with her ex every day.
* WriteWhoYouKnow: Darren Star based Brenda and Brandon's sibling dynamic on his relationship with his own sister. Andrea is based on his friend, Andrea King, who is also a TV writer and producer.
* YouLookFamiliar: ''Melrose Place'' actors Creator/LauraLeighton and Creator/BrookeLangton appeared as different characters; Sophie Burns and Suds Lipton, respectively. Especially odd (or funny in hindsight) in Leighton's case, considering that her ''MP'' character Sydney had supposed died a year before her tenure on ''90210'', which would turn out to have been faked when the reboot of ''MP'' aired in 2009.
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!!The 2008 reboot series
* TheDanza:
** Ryan Matthews is played by Creator/RyanEggold.
** Riley is played by Creator/RileySmith.
* DawsonCasting:
** The reboot's original teen cast consisted of Shenae Grimes (18), Tristan Wilds (19), Anna Lynne [=McCord=] (21), Creator/DustinMilligan (23), Creator/JessicaStroup (21), Michael Steger (28), and Jessica Lowndes (19). Steger was older than Ryan Eggold (24), who portrayed the kids' ''teacher''. Plus adding from season 2, Trevor Donovan (''30'') portraying a ''16-year-old''.
* DyeHard: Silver is a natural blonde like her mother Jackie, but is a brunette for the entirety of the series save for when she briefly dyed it red.
* ExecutiveMeddling: Season two drops Ethan and focuses a lot more on the new characters rather than the old cast. That's cleverly done for Kelly's mother's funeral as it's not shown and Silver comments that a lot of people who knew her but she didn't know attended.
* FakeAmerican: Shenae Grimes is Canadian and had just got off of ''Series/DegrassiTheNextGeneration'', a long-running Canadian teen drama that may have inspired the original 90210.
* FakeBrit: Creator/BlairRedford who plays Oscar is not British.
* FakeNationality: Michael Steger is a mix of several nationalities but Iranian (or anything Middle-Eastern) is not one of them.
* TheOtherDarrin:
** Rather than bringing back Mercedes Castner to play Silver, she was played by Creator/JessicaStroup.
* RealitySubtext: The SequelSeries had a particularly harrowing example for Anna-Lynne [=McCord=]. During filming of the scene where Naomi is raped, [=McCord=]'s castmates simply thought that she was a really good actress, not knowing that [[http://www.cnn.com/2014/05/29/showbiz/celebrity-news-gossip/annalynne-mccord-sexual-assault/ she had actually been sexually assaulted herself]] when she was eighteen. Her breakdown and tears during that scene? She wasn't acting -- she was having legitimate flashbacks to her rape.
* YouLookFamiliar: Rob Estes (Harry Wilson) was Kyle from ''Series/MelrosePlace''.
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