When fans first saw the outfits in the new adaptation of “Mean Girls,” they were not shy about sharing their opinions on the film’s pink miniskirts and mesh bustiers.

On social media, some criticized the costumes for looking cheap, like they came from fast-fashion retailers. Others felt that they did not sufficiently capture the Y2K style of the original “Mean Girls” from 2004. One online commentator even said that the costumes seemed like a clumsy attempt by an A.I. image generator to answer the question: “What do trendy teenagers wear today?”

The wardrobes for the film, released on Jan. 12, were designed by Tom Broecker, the costume designer for “Saturday Night Live.” Mr. Broecker, 61, was not involved in the original “Mean Girls” but joined the adaptation crew after working with Tina Fey and Lorne Michaels on costumes for “S.N.L.” and “30 Rock.”

Mr. Broecker admitted that the criticism of his work made him “super, super, super anxious” for the new film’s release. His goal was to reference the original film’s wardrobes while imagining how its high-school-age characters might dress as members of Gen Z.

He used the “sexy Santa” costumes for a holiday talent show scene as an example. In the adaptation, those outfits were influenced by Ariana Grande’s music video for the song “thank u, next,” so he made them a little more sparkly than the plasticky red skirts in the original.

More than 600 looks were created for the adaptation by Mr. Broecker and his six-person design team. In the edited interview below, he explains how they came up with the wardrobe — which, he said, should not be judged by trailers and teasers alone.

“You’re only getting the bread crumbs,” he said, “when you really want to have the whole 10-course meal.”

What did you think of the costuming in the original film?

When I saw it then, I thought, This is fun, this is high school in 2004. Watching it now, I go, Oh my God, those poor girls were so sexualized. But that’s 2024 eyes looking at 2004. I know they didn’t feel that way at all, but you look at it now and realize that the world has changed.

Where did you look to find inspiration for how Gen Z is dressing?

We were very influenced by Instagram and TikTok, and by celebrities like Billie Eilish, Jenna Ortega and Sydney Sweeney. I have a niece who graduated from high school in Indiana last year. I looked through her closet and her Instagram. And I live near N.Y.U., so packs of students walk by my apartment all the time in light-wash, straight-leg jeans, white Nike sneakers and crop tops.

What did those references reveal about how people dress now?

The early aughts are very influential in the visual landscape of clothing right now. Sometimes I would show Tina certain things and she’d say, Oh my God, I think I wore that before.

Other things have changed. Gender fluidity is a big thing for kids. And everyone wants to be comfortable, especially after the pandemic. So I dressed the high schoolers in the movie in athleisure, like North Face, Patagonia and Champion hoodies.

Fast fashion has changed how young people shop. How much of that did you include?

Probably more than we should have. Two brands we used were Cider and Princess Polly. I stayed away from Shein, but I did find a piece or two secondhand.

I kept saying that we have to get into the mind of a high-school student, and that’s how they shop. The directors got rid of a mall scene that was in the original because kids don’t go to the mall anymore.

How did you differentiate costumes for the Plastics — the three popular girls — from those for the students they reign over?

Everyone in the high school has big bags and sneakers, except for the Plastics, who have little purses and heels. They are different than the people who are weighed down by their books and grounded to the floor with their shoes.

Did you spend more of your budget on clothes for the Plastics?

Basically the Plastics got all the money. For Regina George (Reneé Rapp), we did Isabel Marant, streetwear like Off-White and a lot of vintage stuff. Tom-Ford-era 1990s Gucci was the inspiration for her homecoming dress.

Why do you think people have reacted so strongly to the costumes in the adaptation?

I didn’t realize the nostalgia for the original. It’s hard to have something stand on its own when something exists that people love. But this is not that, and 2024 is not 2004. We have changed how we feel about a lot of things. As the tagline says, this isn’t your mom’s “Mean Girls.”