Mean Girls is called Mean Girls because The Shawshank Redemption was already taken.

Just kidding. Mean Girls is filled to the brim with girls behaving badly; that's where the title comes from. Regina's a self-absorbed manipulator. Cady turns into a shallow schemer and then back into a human being. Even Janis is a self-confessed mean girl.

Mean girls rule North Shore High School, and the movie Mean Girls is an exploration of how and why that happens as experienced by Cady, public school newb.