Mean Girls is an institution. It’s difficult to think of a movie that’s affected the cultural conversation to the same extent, from celebrating October 3rd to yelling “she doesn’t even go here!” in public places, and certainly not one from the dreaded early 2000s. Even for those who normally wouldn’t go near a fluffy teen comedy, Mean Girls is the one. Not bad for a movie whose insane reach even its own director still can’t quite comprehend.

Mark Waters’ brother, Daniel, actually scripted fellow cult favorite Heathers, so it shouldn’t be too surprising teen comedy chops run in the family. Indeed, the infamous “I love my dead gay son!” joke from that beloved, Winona Ryder-starring film is honored in Mean Girls’ lovable Damien, who’s been really busy with choir but is too gay to function regardless.

The religious home-school joke in Mean Girls’ opening moments (“so man could kill the dinosaurs… and the homosexuals”) is a shock to the system. It’s edgy, it’s out there and it’s quite different for a movie in this genre, where easy comedy, about nerds versus cheerleaders or dudes embarrassing themselves while also gaining classmates’ favor by eating all the disgusting cafeteria coleslaw, reign supreme.

Mean Girls has some serious bite thanks to a tight script by comedy heavyweight Tina Fey, who also plays the kindly but whip-smart Ms. Norberry. Originally, the film was slapped with an R rating due to a joke about a certain classmate (Amber D’Alessio — the students’ names are so fantastic in this movie) performing a sex act on a hotdog. The punch-line was watered down so the film could achieve a PG-13 rating and be seen by as many of its core demographic target as possible. This is the same fight filmmaker Bo Burnham had with the recent Eighth Grade, meaning Waters’ argument about the MPAA being sexist still rings true all these years later (Burnham’s film is also a female-fronted teen movie).

The one joke the Mean Girls director refused to cut was about a female student with a wide-set vagina. Waters’ filmography is proudly feminist and female-focused, as — by his own admission — he finds women “much more interesting than dudes.” He wouldn’t compromise on the nitty-gritty stuff, which is where the real comedy comes from. Still, it’s Fey’s writing that solidifies Mean Girls as a true women’s film — by women, for women and led by women. Gretchen’s line about the rules of feminism is a great joke (it’s since become a meme, along with everything else), but this is genuinely a feminist movie. That line exemplifies its message, which is all about kindness. In particular, as Ms. Norberry chastises the junior women, it’s about stamping out girl on girl crime.

The tortured math teacher is one of several finely drawn adult characters, all of whom impact the plot in some way while never stealing focus from the teenagers. Like all the best high school movies, Mean Girls includes a cast of terrific character actors including Saturday Night Live’s Tim Meadows as Principal Duvall, Ana Gasteyer and Neil Flynn as Cady’s well-meaning but often hilariously clueless parents and, of course, Fey’s long-time BFF Amy Poehler as Regina’s horrifying mother (a character so famous she was referenced by none other than Kylie Jenner in an Instagram caption — the highest honor in modern, polite society).

The younger peripheral characters are all hugely funny, idiosyncratic creations in their own right too, much like 10 Things I Hate About You’s iconic Bogey Lowenstein. Their frank to-camera interviews establish the various odd personas, while Janis’ breakdown of cafeteria seating based on social standing is a crucial element to further establishing the greater North Shore ecosystem that doesn’t overplay its hand (though, annoyingly, there are no Goth kids).

The most enduring high school movies feel as though they’ve just dropped in on a random day, with life carrying on as normal. Even though Mean Girls follows a new student, giving the film full rein to load up on exposition, most of the important info is communicated visually or via Cady’s interactions with friends and frenemies alike. Fey and Waters don’t waste time explaining who people are when they can instead make a running joke out of it (“She met John Stamos on a plane,” “And he told her she was pretty”).

The strangest stylistic choice Mean Girls makes, which sees Cady hallucinating various African-based wildlife interludes, pays off in a big way when the entire junior class starts, quite literally, ripping each other’s hair out. It’s the boldest and biggest risk the film takes, but it makes absolute sense. The whole way through, Mean Girls hints that things are about to kick off, and when they finally do, it’s spectacular and hilarious in equal measure.

Likewise, the lecture the ladies are given by Fey’s Norberry happens as a result of this final fight. The change has to come from within, once things have escalated to the extent they can never be the same again. This is a major female empowerment moment, as the math teacher encourages the female students not to call each other “sluts and whores” because it just makes it okay for guys to follow suit.

At its core, and in spite of its title, Mean Girls is about female friendship, and how it’s cooler to be kind rather than cruel. Even the dashing Aaron Samuels isn’t really the endgame. In fact, the issue is with Cady feeling she has to change for him when clearly that’s not the case. The movie’s sunny denouement is aspirational but satisfying, neither saccharine wish fulfilment nor cynical about-turn. Everybody doesn’t magically change either as Gretchen remains a follower, relegated to a new clique.

Waters’ film isn’t as groundbreaking as Heathers, with its school shooting plot still stomach-churning three decades later, but the movie’s cultural impact is no accident. A considerable amount of care and attention to detail has gone into making the world of Mean Girls feel as real as it does. A film of its ilk doesn’t spawn as many memes as this — arguably more than any other in recent memory — even if they’re just from smaller character moments.

It helps that the performances are universally brilliant. Rachel McAdams and Amanda Seyfried are clear standouts, and both deservedly went on to be accomplished dramatic actresses in their own right. Regina’s weight gain is a bone of contention (nowadays, even a size 5 would be considered big, as evidenced by Andy “6” Sachs in The Devil Wears Prada, which was released just two years later), but it leads to subtle touches like how she’s suddenly drinking full-fat Coke while the rest of the Plastics sip Diet.

McAdams, who was subsequently Oscar-nominated for her role in Spotlight, was reportedly cast as the Queen Bee because she’s so nice in real life, and it takes a kind person to play mean. She, Seyfried and Lacey Chabert (as Gretchen) adopt breathy, affected, super-sweet voices to portray the nastiest bitches in school. In contrast, Lizzy Caplan’s deadpan Janis speaks in a gravelly tone, making her delivery of “your mom’s chest hair!” immediately followed by a friendly “I’m Janis” even funnier. Where her alt-chick character would’ve been the butt of the joke 20 years ago (even 10 Things I Hate About You’s Kat Stratford isn’t as evasively arty as Janis), Mean Girls gives Janis a big hero moment, buoyed by her classmates’ gratitude over Regina’s take-down.

It’s yet another massive female empowerment moment, reinforcing Fey and Waters’ message about the importance of kindness and being yourself — hardly anything new, but in this context, their encouragement feels both fresh and necessary. Ruling the school as Queen Bee isn’t important, but having real friends and being true to those people is, and everything will run smoother if everybody just accepts that reality and behaves accordingly — optimistic, but not sickeningly or naively so.

For Ariana Grande’s hugely popular “Thank U, Next” music video, she portrayed Regina while her Victorious cast-mate Elizabeth Gillies was lumbered with the massive, oversized pink shirt as Cady. It was another major example of how Mean Girls has infected the zeitgeist, even now, 15 years after the film’s initial release. It’s the most talked-about element of a video that also takes in beloved movies like 13 Going On 30 and Bring It On, and for good reason. Mean Girls is universally adored.

Mean Girls might be a teenager itself now, but the movie’s popularity continues to grow as a whole new generation falls in love with its cast of crazy characters, messages of inclusion and impressively high joke rate. Rather than the lack of social media dating it, the IRL standoffs in the film — including the infamous three-way phone attack — afford it a lovely timelessness. Another movie may come along five or 10 years from now and provide a whole new host of “that’s so fetch” or “why are you white?” style reference points, but looking back on the last decade and change, nothing even comes close to the fiercely female-focused and endlessly quotable highs of Mean Girls.