Answer by Katy Donahue, Georgetown senior:
Mean Girls is a cornerstone of the collective "millennial" (or whatever your preferred term is) cultural references. Its enduring place as a cultural reference is due to many factors, mostly surrounding its quotability—it has survived, 10 years later, because people are still constantly quoting it. Here are some reasons for its quotability, which is the major reason for its cult status:
It's funny. Written by Saturday Night Live alum Tina Fey, it features many one-off lines and situations that are hilarious.
It's distinct. The lines from Mean Girls are distinct enough to stick in your mind—lines such as "Her father invented Toaster Strudel" are specific enough to make them easy to remember and repeat.
It's accessible and universal, at least to girls of a certain age. Bullying in middle and high school and power dynamics among female friendships are almost unilaterally experienced by girls and young women, so quotes such as "You can't sit with us!" are not only easy to connect to, but most importantly easy to reuse in everyday life, which reinforces its cultural status.
It's a female movie in an era of cultural comedies that were frequently male-focused (Anchorman, Zoolander, Wedding Crashers, etc). Most of the oft-quoted lines from the early 2000s were from male-dominated movies, so Mean Girls had the distinct advantage of a niche movie type, female-centric comedy, that easily catapulted it to the top of this nonexistent but necessary category.
More questions on Cult Films: