In some digital corner of the smartphone belonging to makeup artist Vasilios Tanis lies an impromptu photo spread ofKathryn Hahn striking glamour poses in the back of an abandoned subway train car located near the soundstage forAgatha All Along in Atlanta. The actress couldn't help herself. TheTiny Beautiful Things andMrs. Fletcher star was painted all in green and dressed as the Wicked Witch of the West fromThe Wizard of Oz.

"Which was also a childhood dream come true," Hahn tellsEntertainment Weekly of her getup that was all for a particular episode of the upcoming Marvel series, a sequel toWandaVision (2021) that hits Disney+ on Sept. 18.

Her costarPatti LuPone, in turn, was decked out as Glinda — puffy pink gown, silvery crown, and all. "I think I speak for a lot of us, we were breathless when we got to see Patti as a good witch for that first time," Hahn recalls. "It was so dear and perfect, and just the sweetest thing — not words that you would normally [use to] describe this powerhouse on a stage."

WandaVision, which starredElizabeth Olsen as the Scarlet Witch/Wanda Maximoff and first introduced Hahn's Agatha Harkness as an ages-old enchantress of great power, structured each episode around a classic era of Golden Age television, from the black-and-whiteI Love Lucy days to the video confessional-styleModern Family sitcom. The creator ofAgatha All Along now explains how the sequel takes its inspiration from the iconic witches of pop culture, including Elphaba and Glinda.

"We're a little squirrelly with it," showrunner Jac Schaeffer, who also spearheadedWandaVision, tells EW. "We take some liberties."

EW can exclusively provide a deeper look at one such witch look that the magical cast will channel. InAgatha All Along, the titular sorceress breaks free from the spell Wanda used to trap her in Westview with a little help from a mystery goth kid referred to simply as "Teen" (Heartstopper's Joe Locke). Agatha is now determined to regain the power Wanda stole from her. She assembles a coven — including LuPone's divination witch Lilia Calderu,Sasheer Zamata's potions expert Jennifer Kale, Alice Ahn's protector witch Alice Wu-Gulliver,Aubrey Plaza's warrior witch Rio Vidal, andDebra Jo Rupp's Westview resident Mrs. Hart — to walk the Witches' Road, a mystical realm that presents its visitors with a series of trials.

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If they fail, they die. If they succeed, their deepest desire is granted. It also doesn't seem like a coincidence that the Witches' Road looks like a darker twist on the Yellow Brick Road.

Each of the trials places the coven in a different attire that emulates a particular kind of witch from pop culture. As seen in EW's sneak peek, one such trial involves them dressed as "aFleetwood Mac-style band," Schaeffer explains. "We're in 'Season of the Witch' and that kind of thing. It doesn't have that same abundantly clear thread, but it was our system to be able to pull that fun into the show." And because Agatha's coven is in theirSteve Nicks, "white witch" era for this particular trial, there's singing involved.

"There's so much detail in every set. Even the fact that it's a five-sided room," Locke comments, alluding to the pentagram-shape of the set design. "It is not a musical, but music is definitely another texture to it."

Based on trailers already released, Schaeffer's team also pulls from thePractical Magic-esque witches for one trial, taking the form of WASP-y east coast women in collared shirts sipping wine in a beachfront mansion. "That's my personal brand of ladies in their coastal grandma chic that are backstabbing and duplicitous and fighting for spots at the private school," the showrunner says. "Those are witches. That's a coven." Another trial sees the cast dressed as '80s summer campers messing with a ouija board in their bunk house.

Getting this structure forAgatha All Along was "the biggest hurdle" in making the show, Schaeffer admits, saying, "I feel likeWandaVision looks very obvious after the fact." In that flagship Marvel show for Disney+, Wanda visits Westview, where she and Vision (Paul Bettany) are planning to build a home together. In her grief, she casts a spell around the town, trapping the residents in an ever-shifting reality inspired by her favorite television sitcoms.

"With this one, I, of course, wanted to use a similar mechanism and involve pastiche in a similar way because it was so satisfying in [WandaVision] and so fun creatively, but we couldn't just duplicate it," Schaeffer explains. "This system casts a wider net. The world building expands. The first idea was that they would have these trials as witches. In early days, the tests were sort of like, there's a fire trial, there's a water trial. But then, how do we get the illusions in there? How do we get the pop culture in there? Real talk: How do we get the wardrobe and the production design in there? So that was the trick and the guiding light."

Agatha All Along premieres two episodes on Disney+ this Sept. 18 at 9 p.m. ET, followed by a weekly release.