When Amy Clark signed on to design the costumes for Heathers: The Musical, which opens March 31 in New York City, the first thing she did was go back and watch the 1989 comedy on which the new production is based.

Though she was a big fan of the original film and its costumes, she realized that her memory of it wasn’t entirely correct. The Heathers, the triad of same-named high-school divas who give the movie its name, stuck in her mind as paragons of sex appeal. After all, that’s how the plot works: the Heathers had to be sexy, or else they wouldn’t wield so much power over protagonist Veronica Sawyer.

The only problem? The costumes that looked so sexy 25 years ago seemed downright dowdy. “From a contemporary point of view about clothes,” she says, “I couldn’t put that on stage. The audience wouldn’t have visceral reaction to those silhouettes.”

So — as shown in Clark’s sketches — she and director Andy Fickman decided to take elements like shoulder pads and blazers and scale them back, nodding at the ’80s but with shorter skirts and more fitted jackets. That said, they knew better than to mess with the film’s iconic attention to aesthetic detail. “I think they really established a vocabulary and slammed it home the whole time,” Clark says. “The film has this feel of almost being curated, like a museum.”

For example, the precise and meaningful colors of the costumes stuck around: powerful red for Heather Chandler, weak yellow for Heather McNamara, jealous green for Heather Duke and black and blue for Veronica. “She’s the battered and bruised one who actually feels things,” Clark explains.

And then there was the sweatshirt.

The musical turns Martha Dunnstock, a minor player in the movie, into a majorly sympathetic character — and gives her a unicorn-and-rainbow-bedecked pullover that would be majorly (if ironically) cool today. There’s no movie inspiration for the sweatshirt, which had to be specially made for the production, but that doesn’t mean the designer conjured it from thin air: “Her costume is 100% based on my favorite outfit that I wore probably every other day in 1984,” she says. “That unicorn was my entire life in 1984, though I was lucky enough to grow out of it. That outfit — there’s something so heartbreaking about it.”

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Write to Lily Rothman at lily.rothman@time.com.

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