Survival
Mean Girls makes an extended comparison between public high school and the jungle. Cady imagines teenagers as wild animals at several points during the film, which foreshadows the actual chaos that the Burn Book unleashes. The film depicts Cady's first day as essentially a minefield through which she must perform socially fraught tasks like choosing which desk to sit at, and who to talk to at lunch. The fact that Cady's parents are research zoologists also ties into the film's larger themes about human behavior and animal behavior. Unlike the physical conflict that animals wage in order to survive, Cady explains at one point that in "Girl World," survival is instead determined by who can be the sneakiest.
Individuality
Mean Girls depicts high school as a pressure cooker environment where every student feels compelled to abide by stringent social norms. Both Damian and The Plastics discourage Cady from joining the Mathletes and pursing her mathematical ability, calling it "social suicide." The bylaws of The Plastics in general render all individual decisions subject to the approval to the rest of the group, which makes true individuality impossible. Ironically, Cady's attempts to become more conventionally appealing drive her love interest away, who is more attracted to her quirks. The characters Damian and Janis, especially in their purple tuxedos at the film's end, represent the spirit of the individual over the norms of the crowd.
Popularity
Popularity in Mean Girls is tantamount to power. Because The Plastics are the most popular girls in school, Damian calls them "teen royalty"—a metaphor that captures how in large public high school settings, the many idolize the few. A montage of rumors about Regina conveys to the viewer how she holds the entire school in a thrall of worship and fascination. The Plastics are revolting to Janis and Damian, although Damian reserves a certain fascination for the "fabulous" glamour that they project. Cady realizes that in "Girl World," the key to popularity is often to promote infighting and back-stabbing among one's friends, leading her to conclude that the costs outweigh the benefits.
Femininity
Mean Girls is specifically a story about girls and female friend groups. The male characters in the film remain largely unaware of the complex layers of deceit unfolding in the world shared by the many female characters, which Cady nicknames "Girl World." Cady quickly realizes that high school popularity is contingent upon performing femininity in a rigidly systematized kind of way—for instance, being required to wear pink on Wednesdays. Regina's bedroom resembles a stylized Barbie house, a shrine to the kind of commercialized, traditionalist aesthetic of female beauty that prevails in American culture. Cady, who wears her hair in a ponytail and has little interest in fashion at the start of the film, is wearing sleek dresses from the mall by the end, having been educated in the sexist process by which conventional feminine gender performance affords greater social power.
Intelligence
Cady excels at math, something which Damian notes early on when he reads her schedule and sees she is taking Calculus. Cady's intelligence, which Janis and Damian value, is in fact sometimes a liability when hanging out with The Plastics, such as when Cady calculates the number of calories in Regina's lunch and draws blank stares. Karen is a character who also proves that stupidity can be a greater asset to popularity than intelligence. Ms. Norbury tries throughout the film to "push" Cady toward her full potential as a student, against Cady's attempts to fail math as a way to get close to Aaron. Cady's decision at the end of the film to attend the Mathletes championship, which she wins for her team, represents her decision to embrace her own intelligence and leave more superficial matters behind.
Sexuality
Sexuality in Mean Girls often revolves around how the girls police each other's sexual presentation and behavior. The rules of The Plastics, for instance, seem designed to make sure the girls always look desirable and current in school. Regina uses her blonde bombshell looks to flatten predatory men and manipulate others around her, while airhead Karen only seems to have become popular for her appealing body. In "Girl World," having sex with another girl's ex is off-limits—"That's, like, the rules of feminism!" Gretchen at one point exclaims. Regina and Cady lock horns in the film over Aaron Samuels, with each trying to make the other one jealous by soliciting his romantic attention. The film also portrays high school as a place teeming with illicit sex—Regina cheats on Aaron with Shane Oman in the projection room, where Damian and Aaron also find Coach Carr making out with a student.
Maturity
Mean Girls is about the inner world of teenagers, a sociological group that is often maligned, misunderstood, and stereotyped. To ground her story in reality, Tina Fey read Rosalind Wiseman's book Queen Bees and Wannabes, which contributed heavily to the speech that Ms. Norbury gives the junior girls in the assembly scene. In that scene, Ms. Norbury beseeches the girls to stop calling each other "sluts and whores," and to write out apology letters to one another, in an effort to move beyond the problems plaguing the school. The main gesture in the film that represents maturity is accepting blame: none of The Plastics accept blame for the Burn Book, and in fact actively lie about what they know about it. Only when Cady comes forward and accepts blame for the Burn Book does the film begin to show how she has developed and matured for the better—rejoining the Mathletes, apologizing to those she has wronged, and distributing her Spring Fling tiara to the class.
