Spoiler alert: The singer, 31, appears amid the trippiest sequences in the Ethan Coen-directed thriller-comedy.

In an interview with The Wrap, Coen and co-writer Tricia Cooke detailed why Cyrus was cast as raunchy hippie Tiffany Plaster Caster, a character based on a real-life creator of celebrity penis plaster casts.

“I was telling [Cyrus] about Cynthia Plaster Caster, ‘I don’t know if you know, your character’s based on Cynthia,’

” Cooke told the outlet. “She’s like, ‘I thought that’s why you called me.’ Big fondness for Cynthia Plaster Caster.”

“Miley loves her d—s,” joked Coen. “That’s her thing too. She’s into that, both the retro hippie thing and the whole phallus-molding thing.”

Related: Miley Cyrus Fangirls Over Mariah Carey as She Wins First-Ever Grammy: ‘This MC Is Gonna Stand by This MC’

Miley Cyrus at the Grammy Awards Feb. 4

Cynthia Albritton, known as Cynthia Plaster Caster, died in 2022 at age 74. The artist’s series of works featured casts of famous figures’ body parts, starting with Jimi Hendrix, according to Deadline.

Per Variety, Albritton also produced casts of the penises of MC5’s Wayne Kramer, Pete Shelley of the Buzzcocks, and Jello Biafra of the Dead Kennedys, in addition to the breasts of Laetitia Sadier of Stereolab and Peaches, and Karen O of the Yeah Yeah Yeahs.

Of filming the Hannah Montana alum’s psychedelically infused scenes opposite Matt Damon, Cooke recalled that Cyrus was “just game for anything, whatever you ask her to do.”

“We wanted to do this low shot that was kind of pushing into her and we’re like, ‘Do you mind if we go down here?’ She’s like, ‘I’ve done much worse.’ ”

Coen added, “She is so much fun… At 29 years old, she’s — I mean it in the best sense — like an old show-business broad. ‘Yeah, whatever, honey. All you need.’ ”

Wilson Webb/Focus Features

(Left-right:) Ethan Coen, Geraldine Viswanathan and Margaret Qualley on the set of “Drive-Away Dolls”
Wilson Webb/Focus Features

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According to Cooke, Cyrus is so “into her phalluses,” she allegedly “has a whole room devoted to phalluses.”

In 2019, the Grammy winner claimed that she was “kicked off” the 2012 family-friendly film Hotel Transylvania after a photo of her with a penis cake for then-boyfriend Liam Hemsworth surfaced.

Drive-Away Dolls stars Qualley and Viswanathan as a pair of lesbian friends trekking south to Florida while toting sensitive materials, including what turns out to be dildos from Tiffany’s plaster casts, in their drive-away vehicle.

In an interview with Collider last June, Cooke called the film “a queer kind of caper that doesn’t take itself too seriously, and that’s very lighthearted and fun and kind of outrageous at times… all of those things.” Coen added: “And a little sex.”