One distinct theme that both films share is the role of the "outsider." In both films, the outsider is someone who must try to gain social acceptance. The protagonists in both films are the outsiders of the settings in which they are forced to live. Poppy Moore is from Malibu and is thrown into the setting of the British boarding school. She is an outsider to the norms and social understanding of Abbey Mount, and immediately crosses paths with Harriet. Cady Heron enters her public school setting and is completely unaware of the conditions that surround her. For Cady and Poppy, they enter as the outsiders. Their source of gaining strength comes from legitimate acceptance from the larger group. Both films display the importance of social acceptance as part of the adolescent's internal sense of understanding. Cady and Poppy must "face the music" in terms of social judgment in order to find a sense of personalized actualization. When they are accepted by their peers, they are able to find happiness. In both films, the outsider must endure a "trial by fire" in order to become part of an established group of insiders.
Another theme that is present in both films is the presence of a feminine antagonist. Both films display the feminine antagonist as one who provides significant challenge to the protagonist. Harriet is actually quite driven to ensure Poppy learns her place. Some of the things she does are borderline criminal, such as starting the fire. Hacking into the email account and ensuring that the public perception is against Poppy is reflective of how strict social norms that the outsider must "follow" are enforced. Her role as the antagonist is to preserve the social order in which she is "head girl." The social order is something that Regina George and the Plastics invented. It is a world that Cady learns quickly carries power with it. Regina is the female antagonist that Cady must learn to navigate. Regina enforces the rules over Cady, only to become subverted by it in the process. In both films, the feminine antagonist seeks to reaffirm a social structure that is challenged by the presence of the protagonist.
Finally, a theme could be the almost ornamental manner in which boys are depicted. Contrary to traditional depictions, the protagonists' affinity for boys is part of a larger process of finding themselves. Traditional depictions would feature the girls removing all else for the boy that captures their fancy. Yet, Poppy and Cady both recognize that boys are a part of their social being, something that is more sidebar distraction from the central issue of social assimilation. When both girls struggle with the idea of social acceptance, their affairs with boys are reflective of this struggle. Poppy's daliance with Freddie and Cady's desire for Aaron are not all encompassing. The girls' challenges in this domain is reflective of the larger challenges they face. Boys are not sources of salvation. Rather, they are extensions of social complications.
Both movies have strong female leads. While Cady begins Mean Girls as an easily mendable mind, she quickly grows confidence in herself and her opinions. Poppy is a very outspoken girl throughout her entire story, but learns to use her strength of character in better ways. The two movies are about growth and learning while trying to navigate through a difficult time in a young girl's life: high school.
Another important theme is the power of friendship. Cady makes wonderful friends, but ends up stabbing them in the back for girls who will never truly accept her for who she is. Poppy has trouble with the girls at her new school at first, but as she grows, she becomes a better person and connects with them.
Most movies these days about high school girls have similar plots and themes: the girl has friends, makes bad decisions, meets a guy, gets the guy, realizes she still needs her friends, and ends up a better person than the girl at the beginning of the movie. Mean Girls and Wild Child are no exceptions.