CNN
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When the trailer for Greta Gerwig’s “Barbie” movie was first released, Google Trend searches for fluffy Mules shot up 115 percent. This was, of course, largely inspired by the trailer’s scene featuring Margot Robbie’s Barbie stepping out of her pink stilettos and into a tip-toe pose, a reference to the doll’s signature stance due to her perpetually frozen feet. (In 2015, Mattel began making Barbie dolls with adjustable ankles so she could finally relax — and wear flats.)

With a wardrobe now spanning 64 years worth of fashion, she’s had her pick of footwear, but Barbie has been closely associated with the stiletto mule — also called the stiletto slide or sandal — since her inception.

It’s clear that shoes are an important totem in Barbieland; in the movie, Barbie’s feet, or what happens to them, serve as a key plotline. When it becomes clear that her arches have fallen, it’s a bad omen. When she seeks wisdom from Kate McKinnon’s Weird Barbie, she must choose between pink pumps or brown Birkenstocks, seemingly à la the infamous red pill-blue pill dilemma in “The Matrix.”

And throughout the film’s meticulously thought-out press tour, Robbie has been knocking out look after Barbie-themed look, with designer pieces frequently paired with high-heeled mules custom designed by Manolo Blahnik — like a take on the 1964 “Sparkling Pink” Barbie, for example, which Robbie replicated for a press conference in Seoul, South Korea.

“When you walk in mules, you walk a bit differently…Madame de ­Pompadour in her mules, walking around Versailles, click click click,” Blahnik once quipped. “Can you think of anything more exquisite?”

Mattel co-founder Ruth Handler introduced Barbie to the world in 1959, changing everything the world then knew about girls’ dolls. The doll’s inspiration was somewhat controversial, coming in part from the German comic strip character Bild Lilli, a sassy high-end call girl who was later sold as an adult novelty doll. A model in many respects, Barbie had breasts and an anatomically impossible figure, and wore a fashion-forward look created by Mattel designer Charlotte Johnson: a black and white striped bathing suit paired with backless heels.

“It was almost like a slide, so it’s very revealing, but then you have this really thin high heel,” explained Elizabeth Semmelhack, Director and Senior Curator at the Bata Shoe Museum in Toronto, of the shoe’s design. “It was instantly linked to ideas of feminine desirability. Not only does the stiletto heel race into fashion at this time, but Barbie does as well.”

“Our mules are still used on Barbie,” Mattel’s Kim Culmone, SVP of Barbie Design, told CNN. “Less so on dolls targeted to kids because they fall off and lose them — we do keep playability in mind, but the open toe backless shoe style is used on collector dolls and in reproductions.”

The mule has both a storied and complex history, and has “for centuries been connected to ideas of play, private time, and intimacy,” said Semmelhack. According to Semmelhack, backless slippers first became more ornately designed for upper-class women in the 1600s. In the 18th century during the Rococo period, culture in Europe grew more focused on more intimate gatherings, so the mule functioned similar to the way a house slipper would. (A pair of silk mules belonging to Marie Antoinette sold for $57,000 in 2012.) “These elements of dress that had previously been worn, just in the privacy of one’s boudoir, start to become a little more appropriate, not for fully formal occasions, but for a wider range of them,” she said, adding that “they basically signaled that you were a little more relaxed.”

The heeled mule came back into women’s fashion in the middle of the 19th century, as part of a wave of nostalgia for 18th century style. “At that point, they still continued to signify the kind of private domestic realm,” Semmelhack continued, “so the backless mule was kind of equivalent to being in a state of undress.”

Erotic photography came about in the 19th century, and Semmelhack points to depictions of women wearing nothing but heels, which increased the hypersexualization of the high heel in the following decades. (In Edouard Manet’s famous 1863 oil painting “Olympia,” for example, a woman lies on a bed, wearing nothing but yellow mules.) “You add in the peep toe, which came in in the 1930s, then fast forward to the post-war period of the 1950s, and you’re starting to see the back of the foot and the toes of the feet,” she explained. “It also gets interpreted as a boudoir slipper, and the quintessential Frederick’s of Hollywood shoe. By the 1950s, the height of a heel begins to skate towards the tawdry.”

When it comes to the stiletto heel, exactly who invented it and when is a bit murky, but it’s clear there was a move towards a sharp, sleek look in the 1950s, Semmelhack said. She credits designer André Perugia as the one “who was playing with metal first as something that can support a woman’s weight.” Though it doesn’t look like today’s stilettos, his 1951 “needle heel” sandal featured a four-inch steel heel held together by three thin rhinestone bands.

Like Barbie, the stiletto mule also has strong ties to Hollywood. In the 1950s and 1960s, Marilyn Monroe, Barbara Eden, and Jayne Mansfield all wore high-heeled, open-toe mules. Mansfield, in particular, was frequently photographed in a bathing suit and heels, much like the original Barbie. Many were Spring-o-Lators, an invention from legendary shoe designer Beth Levine that featured an elastic strap to keep a wearer’s feet from slipping out while simultaneously preventing the unwanted “clack-clack” sound that occurred while walking.

In the years since, the stiletto mule has wavered between being garish and glamorous in popular culture — and it encompasses both. One thing’s for sure, the shoe makes a statement. In John Waters’ 1974 film “Female Trouble,” it was her parents’ refusal to buy the heels that caused Divine’s Dawn Davenport to run away and commit crimes. (“Nice girls don’t wear cha-cha heels!”) In his book “The Satanic Witch,” Church of Satan founder Anton LaVey, who had a controversial friendship with Mansfield, referred to the shoe’s “daring” and “cheap” reputation, saying “only the most thick-skinned of witches can feel comfortable wearing such a style shoe.”

Then there’s Peggy Bundy, who wore stiletto mules in “Married With Children;” it was actor Katey Sagal’s idea to doll her character up, she told Terry Gross in a 2012 “Fresh Air” interview. “She should look sexy… those kinds of shoes make you walk a certain way.” Debbie Harry wore mules on the cover of Blondie’s 1978 album “Parallel Lines.” Olivia Newton-John wore red Candie’s stiletto slides at the end of “Grease.” Dolly Parton has also worn them for years; Hollywood Billboard queen Angelyne wears them to this day.

In the early aughts, the stiletto mule experienced a particular resurgence, thanks in part to a brand called Polly of California that manufactured mules for fashion designers like Betsey Johnson, who put Playboy Playmates in an ankle-strapped version of the shoe on the runway for her 2001 Spring-Summer show. Polly mules were known as the eight-hour heels, since their foam-padded insoles and platform wooden base provided enough comfort to wear all day.

Hollywood retail landmark Trashy Lingerie also carried Polly shoes for years, even offering bespoke options for customers — and made the stiletto mules Jessica Simpson wore as Daisy Duke in 2005’s “The Dukes of Hazzard.”

Owner Randy Shrier told CNN the shoes were “truly an art form” because of original shoemaker Armando Barasa’s complex process. Some of the die-hard Polly fans ended up having 10 or 20 custom pairs, he said. “Once they got one or two, they’d go crazy and start buying all these different color combinations.” Polly of California went out of business years ago, though the vintage shoe brand Re-Mix in LA currently makes the same style, called the Hollywood Stilettos Slide.

And today, with Barbiecore a trend du jour across much mainstream culture, it’s poised for a serious comeback. (Shoe brand Aldo released a Barbie-themed collection in partnership with the movie that features a mule style, though its heel is more kitten than stiletto.) Beyond Robbie, A-Listers including Jennifer Lawrence and Rihanna have recently been seen in the shoe. Coco Fong and Valerio Bava, co-creative directors at the high-end shoe brand Malone Souliers, have also noticed increased interest: “It’s reminding us of how iconic a heeled mule is,” they told CNN. “The Barbie mule especially feels so glamorous and nostalgic.”

In other words, just like “Barbie” is a film about a doll breaking out of her box, it’s time to break a pair of mules out of theirs.