* AbilityOverAppearance: Lizzy Caplan almost didn't get the job, as the producers thought she was too pretty to play [[CoolLoser Janis]]. As such they gave her a more goth/alternative look rather than trying to dress her down.
* ActorSharedBackground: Betsy Heron gets offered tenure at Northwestern. Her actress Ana Gasteyer's alma mater is Northwestern.
* BillingDisplacement: When a Mean Girls game came out for the Nintendo DS in 2010, Lindsay Lohan, the film's star, wasn't on the cover. The tabloids had a field day with this. Ana Gasteyer who plays the minor role of Cady's mother is also credited before Lacey Chabert and Amanda Seyfried, two of the protagonists.
* CaliforniaDoubling: As Creator/RogerEbert [[http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/20040430/REVIEWS/404300306 put it]], "She enrolls in Evanston Township High School -- which, like all American high schools in the movies, is physically located in UsefulNotes/{{Toronto}}"
* ContractualPurity: The film's R-rated content was toned down when Lindsay Lohan was cast, as she was considered too family friendly for such a raunchy film. Likewise Lohan opted to play Cady rather than Regina, worrying about hurting her 'good girl' image.
* DawsonCasting: Regina George is played by Rachel [=McAdams=], who was 24-25 at the time of filming. Also, Lacey Chabert and Lizzy Caplan were both 21 when the film was made. Lindsay Lohan and Amanda Seyfried, however, were both teenagers at the time.
** In the sequel, two of The Plastics - Mandi and Chastity - were played by actresses who were 22 at the time. Was subverted with Jo, Hope and Abby, played by actresses who were around the characters ages during filming.
* DeletedScene:
** Cady tries to give Regina a WardrobeWound by having a friend rig her cafeteria table so that it tips and spills food into her lap when she sits down. However, Karen sits where Regina was supposed to, thus becoming the prank's victim.
** Cady rigs the weighing scales to fool Regina into think she's lost weight.
** An extended version of Cady at Aaron's house where it's revealed it's only him and his mother.
** An ImagineSpot during the assembly where Cady imagines that Ms Norbury says "your parents have been eaten by cannibals!"
** A longer version of the scene with well wishers at Regina's bed. Her mother tells the congregation that Regina lost so much weight from being immobile that the doctors recommended Kalteen Bars. Regina gives a BigNo and the army of people rush outside just as Cady comes to the door. She throws the bouquet of flowers inside as she's swept away by the crowd.
** Just before going into the Spring Fling, Cady bumps into Regina in the bathroom. Regina says she's over the whole thing.
* FakeAmerican:
** Rachel [=McAdams=] who plays Regina is Canadian.
** In the sequel, Chastity is played by Australian actress Creator/ClaireHolt.
* ImageSource:
** GirlPosse
** MakeWayForThePrincess
* MeanCharacterNiceActor: Rachel [=McAdams=] is the polar opposite of Regina, the crew made a point to cast the politest actress as the meanest character.
* PlayingAgainstType:
** Neil Flynn, who was at this time well known as the [[{{Jerkass}} sarcastic smartass]] Janitor on ''Series/{{Scrubs}}'' plays Cady's loving, caring, affectionate and utterly clueless father.
** Retroactively for Amanda Seyfried who eventually became known for playing wholesome GirlNextDoor types. Playing a BrainlessBeauty who makes out with her first cousin is a tad different. She was nearly cast as Cady, which would have been within her eventual type.
** Director example: Mark Waters usually has supernatural elements in his films. There are none in this.
** Claire Holt was best known on Australian TV as the bossy, responsible Emma on ''Series/H2OJustAddWater'' - making a ReallyGetsAround character like Chastity quite different.
* PlayingGertrude: Amy Poehler who plays Regina's mother is only seven years older than Rachel [=McAdams=]. However it's implied that she's a stepmother (and something of a trophy wife), who has also had some excessive plastic surgery. Ana Gasteyer is a little more believable, with a nineteen year difference between her and Linsday Lohan - but Betsy Heron is implied to have been an established zoologist in Africa when Cady was born. Tina Fey outright says on the DVD commentary that the two actresses are far too young to be mothers.
* ProductionPosse: The movie was produced by ''Series/SaturdayNightLive'' co-creator and producer Lorne Michaels, and written by Tina Fey, who plays a supporting part, and also includes her SNL castmates Ana Gasteyer and Tim Meadows. She's also best friends with Amy Poehlher.
* RealLifeWritesThePlot: Tim Meadows suffered an injury to his hand and required a cast. This was explained as Mr Duvall getting carpal tunnel.
* StarMakingRole: At the time of its initial release, it was considered to be this for Creator/LindsayLohan. In the longer run however, Creator/TinaFey was the one whose career really took off as a result of this film, with Creator/RachelMcAdams and Creator/AmandaSeyfried also benefiting quite a bit.
* UnintentionalPeriodPiece:
** The film is a time capsule of the last generation of American teens who didn't have the internet as an omnipresent force in their lives. The very idea of a "three-way calling attack" could only work with landline phones, which are fast becoming an endangered species today, while one of the symbols of Gretchen's wealth is the fact that she owns a cell phone, an item that became all but a necessity of modern life in just a few short years. Cyberbullying is never even mentioned, even though, by the end of the decade, it would become the [[YouCanPanicNow moral panic]] ''du jour''.
** Additionally, Regina's materialistic lifestyle, despite it being used to help emphasize how empty and hollow her life truly is, points the film to before the Great Recession, when flaunting immense wealth was in style.
* WhatCouldHaveBeen:
** In the original script, Gretchen was envisaged as plain-to-ugly (with a "sniveling whiny face") and part of the in-crowd solely for her wealth. Obviously, this was dropped when the very pretty Creator/LaceyChabert was cast in the role, but traces of the original perception of the character can still be seen in the film in Regina's obvious surprise that Gretchen was nominated for Spring Fling Queen.
** The film was a lot filthier before it was PG-13ified. See {{Bowdleri|se}}zation on the main page.
** Amanda Seyfried was nearly cast as Cady before producers felt she was better for Karen. Lindsay Lohan nearly played Regina but opted to play Cady instead, worrying that playing a mean girl would hurt her wholesome image at the time.
** Scarlet Johansson and Ashley Tisdale auditioned for Karen, while James Franco auditioned for Aaron.
** Tina Fey was approached about sequels for years and refused to do them. When the actual sequel came out - and was met with {{Sequelitis}} reactions - she said she regretted not writing one.
* WordOfDante: [[http://bust.com/mean-girls-10th-anniversary-reunion-cast-spills-secrets.html In an article for "Entertainment Weekly"]], the actresses were asked about what they imagined their characters as.
-->'''Karen:''' Manage or own a store that sells really cool dog attire, like Swarovski dog collars and Halloween costumes for animals.
-->'''Cady:''' In Africa with [[Series/TheOprahWinfreyShow Oprah]] working at children’s schools with family, teaching girls to be nice.
-->'''Gretchen:''' Running the Toaster Strudel Empire. She has curly hair and worked everything out with Jason.
-->'''Regina:''' She’s a [[TheRealHousewives Real Housewife]] and has found all her other Reginas.
----