How the “May December” Wardrobe Spirals from ‘Delicate Princess’ to Creepy ‘Mimic’ (Exclusive)

Costume designer April Napier tells PEOPLE about the nuances in each character's wardrobe

May December, starring Natalie Portman and Julianne Moore, is one of those movies that stays with you well after it ends.

Loosely based on the real-life true-crime case of Mary Kay Letourneau, the movie makes you think about the characters, the real people the story is based on and all the subtle nuances throughout the film — including how something as simple as the characters' wardrobes help to demonstrate a story arc for each.

To the average eye, the costumes in May December look just like regular clothes. Savannah, Georgia-based wife and mom Gracie Atherton-Yoo (Moore) is outfitted in what you'd expect of a woman from the South: pastels, Hill House Nap Dresses and florals. Similarly, Elizabeth Berry (Portman), an actress from the city who is set to portray Gracie in a movie about her life, is more edgy and wears designer pieces in dark neutrals.

But costume designer April Napier, assistant costume designer Hunter Hamilton and Napier's team took everything a step further and got inside the minds of each character, including the complicated brain of Joe Yoo (Charles Melton), to insert the quietest details to make sure each outfit was the perfect one for each character in the Todd Haynes-directed film that's already garnering plenty of award season buzz.

Ahead, Napier takes us through her creative process and describes how she built the characters' wardrobes and how she used them to tell each of their stories — including how one specific piece was part of Joe's breakdown.

Related: May December PEOPLE Review: Julianne Moore and Natalie Portman Face Off in an Unsettling Comedy

Related: Awkward Interview That Loosely Inspired Scene In Netflix’s May December Resurfaces: ‘This Is Getting Weird’

Both Gracie and Elizabeth are very interesting characters because you’re not sure who is the protagonist (if either). Tell us about their wardrobes and the nuances to each. How did you create them?

There's a performative femininity about Gracie, right? She's very brittle, and she's trying to contain something that is on the verge of collapse. She wanted to have a kind of delicate princess quality about her, so we knew that we had to have soft textures. We knew we had to have a palette that was lavenders, pinks, ivories, florals.

I looked at the pictures of photographer, Tina Barney, she has this book called Tina Barney: Theater of Manners. I looked at Deborah Turbeville, who's a fine arts photographer and in the '70s, did a lot of ads for fashion houses. I was looking specifically at one she did for Valentino. We looked at Robert Altman's 3 Women, because that was Sissy Spacek, Shelley Duvall and Janice Rule, and there is all of those lavenders and femininity in there.

We started with Julie, and we had a very short prep period and a short shoot — it was only a 23-day shoot. But we got Julie on Friday, and we mapped out all of her changes, so we knew where everything would fall. She is in lavenders, ivories, pinks, florals. And then the end, of course, with the white dress. We also knew she had one hunting outfit in there.

We then knew that Elizabeth needed to transition to when she starts emulating Gracie. So we knew that Natalie was going to come in as someone from an urban place, it's Los Angeles, it's New York, it's someplace from a city. She kind of has a uniform, as we all sort of do. We used Jane Birkin as a touchstone. She enters and she's wearing that blazer, which is The Row, and jeans, a simple white T-shirt, I think Redone, and then a Celine neck scarf. So that's sort of her uniform.

And then she goes into the Memorial Day party. We knew we wanted to start her in blacks, grays, navies, monochromatic and dark. Todd didn't want her to go to the party in black, because that would've been so disconcerting, and she's trying to kind of fit in. Everyone there is wearing some element of red, white and blue, so she wears that deep burgundy, kind of oxblood-colored slip dress. And she has the Hermès straw hat on.

Related: Natalie Portman Says Working with Julianne Moore on May December Was 'Absolutely a Highlight of My Life'

It almost becomes creepy when Elizabeth starts to dress like Gracie. She really sinks into her. That shot of the two of them in their floral dresses really hits you. They’ve become one, and it's almost creepy.

Yes, it is. Elizabeth’s color palette starts to lighten and soften until you see her in pinks and lavenders. Todd gives us a big list of films that we should look at for inspiration, and one of them was called The Pumpkin Eater. There’s a baking scene in the movie, where the two actresses are in very similar outfits, and I used that as inspiration for when Elizabeth shows up for baking with Gracie.

Gracie's wearing that floral dress with her linen apron, and then Elizabeth shows up and she's like, "Oh, look how nice you look," and she's wearing kind of a mimic of that outfit. Very much like Pumpkin Eater, but it's in a more graphic, like a more urban pattern. And then Gracie bestows upon her the floral apron, so she's got the floral on top.

When you see them outside, when they're watching Joe on the roof, Elizabeth’s really mimicking. She's learning all of Gracie’s language.

There’s also the scene at graduation, in their matching white dresses. Elizabeth is wearing her big Saint Laurent glasses, but you see her crumble. It all falls apart. Her whole shield just dropped. It's insane.

That was in the script. Samy [Burch, screenwriter] had written in the script that they meet together on the field, like two white knights, so we knew that they were going to be in white. You don't always follow the script literally, but on that one, we knew that's where we wanted to be.

So Elizabeth is in a much more architectural stark clean dress, and then Gracie’s more frilly, but they're meeting together. Gracie has a vintage Armani bag, and Elizabeth has her little crossbody. Elizabeth has on her Saint Laurent shades, and Gracie’s wearing the big Celine, but they're more '70s style. And there they are together. Another mimic.

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Speaking of Joe, he definitely feels like a Savannah dad, but you probably had to get into the headspace of a man who had to grow up quickly and leave childhood behind when creating his wardrobe. What was that like?

He's wearing a costume of sorts, trying to fit in, in the south, and there really is a uniform for men there. Everyone has a khaki trouser, a khaki short, an oxford shirt, a blue polo, they wear Sperry Top-Siders. He's playing a role of being a dad, he's trying to play the role of a grown-up. He was a young man when they fell in love. He's Korean, so he's already kind of ostracized from the community. So he's just trying to fit in.

The way he wears the clothes — his posture is really slouchy. And then there’s that scene when he's on the roof. We put him in that striped rugby, an Abercrombie rugby, because that's the place where he is breaking down, and it's like his security blanket. It’s something he's had in the back of his drawer forever. We washed it down and made it filthy, like it's his one thing he's hanging onto, which is so great in that specific scene.

Related: May December Director Says Charles Melton Gained 40 Lbs. for Movie Because His 'Hunkiness' Didn't Fit Role

The costumes in this movie are so subtle. It’s easy to overlook the detail you put in.

That’s the thing about doing costumes. You do a lot of research, and you think really deeply about the psychology of the characters and the environment, where they live, what they listen to.

I like to make costumes that have a really delicate hand, just to support the story. I don't want it to be like, costumes [gestures wildly]. I want it to be very natural, very lived in, very understated. But it has to be precise when you're doing that, so you have to spend a lot of time really dissecting the very place where that thing fits. And that's more in how it fits and the size of it. Is it pressed? Is it schlumpy? There are so many details that go into that. Sometimes with costumes, they don’t shout, but they inform. For this, we had to make sure there were enough twists that it was subtle and off just enough but still quiet.

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