Get in, loser, we're going shopping. 'Mean Girls' costume designer shares what influenced the Plastics' Y2K looks.

So fetch! There's never a wrong time to celebrate the iconic looks of Mean Girls.

Written by Tina Fey, the 2004 teen comedy follows Cady Heron (Lindsay Lohan), a teenage girl who moves from Africa to Illinois with her family as she navigates a new high school, crushes and social cliques, like the Plastics (played by Rachel McAdams, Amanda Seyfried and Lacey Chabert).

Aside from helping to launch the careers of McAdams and Seyfried, the film gave us some of the most iconic lines in teen comedy history that are still spoken by millennials everywhere: "On Wednesdays, we wear pink," "She doesn't even go here!" "You can't sit with us!" "I'm not like a regular mom. I'm a cool mom," and "Boo, you whore," among other priceless gems.

The fandom is especially real when it comes to the film's Y2K fashion. From its vibrant pinks, micro mini skirts, statement T-shirts, Juicy Couture sweatsuits and flannels, the movie's fashion continues to remain relevant nearly 20 years later.

In fact, sales of women's cargo pants jumped 81% from January to May, and sales for biker jackets, denim garments and crop tops have increased significantly at stores like H&M and Zara, according to the Associated Press. Fashion retailer Boohoo released data showing that Pinterest searches for green cargo pants increased by 163% in September, while leather bomber jackets increased by 129%, fur boots increased by 83% and searches for flannel shirts increased by 37%.

Can Mean Girls take credit for the rise of Y2K fashion? Who better to talk about it than the woman who curated the looks herself: the film's costume designer, Mary Jane Fort.

'A costume designer is a storyteller'

Fort took her job seriously from the start. As she explains, that includes doing heavy research on what teenage girls in the Chicago suburbs, where the film is set, were wearing to school at the time.

"I started poring over school yearbooks," she tells Yahoo Entertainment of her early research. "Every part of the country is a little different. And every city has a personality, so I wanted to jump off from reality and then make it into a heightened reality."

Remember, the film was shot before social media. "There were no influencers, none of that existed at the time," Fort explains.

Yet, she wanted to establish the Plastics as being "part of something important." So much so that all the kids portrayed in the school — boys and girls alike — wouldn't just be jealous of them, but they'd literally want to be them.

While Fort says she pulled inspiration from the 1950s when designing the Plastics' attire, her biggest idea came after visiting Dylan's Candy Bar in New York City.

"I was like, 'Oh, that's what everyone likes: candy!" she says. "I decided that that's what I wanted to do with the Plastics. I wanted them be something everyone wanted. They looked good and they shined and their colors were great."

Of the clique's attire, Fort says "I had to look at them all together, and make them one entire piece. They had to balance each other."

As for the rest of the cast, Fort pulled countless options for the actors to scour through. "The Juicy [Couture] sweats were starting to happen, but there was none of this leisurewear fashion that you see now," she explains, noting that the final product — including the miniskirts and Janice Ian's (Lizzy Caplan) goth vibes — was a collaborative experience under Fort's eye.

"A costume designer is a storyteller. And as an artist, you're not working alone. We're working together," she says. "You create the character together."

'Tasteful' in Pink

Growing up, Fort's favorite fashion combo was pink and green. She was elated when she learned that pink was going to be a prominent palette in the film.

That's evident in the iconic scene where the Plastics decide to invite Cady into their world, telling her, "On Wednesdays, we wear pink."

Still, she "didn't want everyone to be drenched head to toe in pink."

"It was about balancing it out and giving everyone something pink that was a part of their particular character," Fort says.

In dressing the actors, she also wanted their outfits to display the character's intention as well.

“In Mean Girls, there's a structure to each character, there's a structure to each costume and there's a structure to each environment," Fort says. "I can't just say, 'OK, here's this and here's this, now get out there.' You have to know what they'll be doing [in the scene]. That's where you can discuss why they should have this or that, which is the part I love."

That includes the scene where the Plastics perform "Jingle Bell Rock" for the winter talent show. The Santa outfits, Fort explains, were designed to be a statement piece.

"I wanted it to be tasteful," she explains. "Those skirts are a rubbery latex fabric, but they're not too short. They're not skintight, and so it's kind of a silhouette from the '50s."

Fort admits she "could have gone a whole different route" for that performance, but looking back she says the choice may be a testament for the film's longevity.

"I think that's another reason, quite frankly, why it does stand up with time," she says. "Now, younger children are so much more advanced than even me, but you can still show it to them and it's not inappropriate."

The Mean Girls legacy

Fort admits she doesn't understand the hype behind Mean Girls fashion.

"I don't really know why," she laughs. "Any project I do, I'm not thinking of it as a fashion statement. I'm thinking of it more as a story. I think other people, the fans, will be better at answering that question than I am."

What she does understand is that good fashion is a time capsule. Film and cinema, she says, help us to "tap into those feelings" from yesteryear and relive them.