Fashion girls were flocking to Foot Locker in March–and they haven't gone too far for summer. Athletic, orthopedic and downright dorky sandals are popping up on the feet of some of the coolest girls I know. We're not just talking about Adidas shower sandals: Tevas and Birkenstocks are also becoming favorites.

Yes, this is a real thing.

This summer, the uglier, sturdier, and more granola your shoes, the better. Vogue Paris, purveyor of all things sexy, chic and French, even styled a whole shoot with Birkenstocks worn with wooly socks. Birks on their own just weren't ugly enough. J.Crew has even commissioned a collab with Birkenstock.

"I have definitely seen a resurgence in ugly footwear," says Man Repeller's Leandra Medine, an authority on all things ugly and cool.

Medine says she's actually been noticing this for a while–and points to the usual suspects (Celine, Miu Miu, Alexander Wang, Giambattista Valli) as the originators of this trend. Even the casual fashion observer probably noticed Celine's furry slides from Phoebe Philo's spring collection, aptly dubbed the "furkenstock." And that casual observer, like many a fashion girl in October, probably remarked on how outlandishly ugly they were. But when Phoebe Philo says jump, the fashion industry asks how high. Just last week, Miley Cyrus was photographed wearing them. And Giambattista Valli's subtler take on the Birk has been selling like hotcakes, according to this WWD article.

"Birkenstocks are definitely making a come back," says Fivestory founder Claire Distenfeld. "I think after several seasons of pure decadence, color, print and non stop patterns, we have a moment of reverting to simplicity."

With high fashion designers embracing the shape, it's no surprise the classic Birkenstock, in all it's $90 glory, is having a moment."I really like the thick straps on my Arizona's, which are blinding white, and scream: I'M REALLY PRACTICAL!" says Glamour Associate Market Editor Laurel Pantin, who has been rocking her Birks all summer long.

As for Tevas, I think we can thank the boys for that one. It was during a presentation at Pitti Uomo a few weeks ago that the trend kind of hit me over the head: Tevas are back. Tommy Ton, who was sitting beside me when I blurted that out, just sighed, "I know." He sounded almost as surprised as I was. In menswear, the trend is in full bloom. Urban Outfitters even released a special Teva collab at the end of May. And now it's starting to trickle into women's.

But really–Tevas and Birks, like Adidas Slides and athletic sneakers, are really part of the same trend. Ugly is in. But why?

Obviously, comfort is an important factor. "Thankfully, I think everyone's a little more comfortable with being comfortable these days," says Pantin.

Comfort is cool now–or, at least looking comfortable is cool. That's the point: It's not enough for shoes to merely be comfortable, they have to scream practicality; it's gotta be a sort of 'fuck you' to fashion–otherwise it's not a statement at all. And then you're just wearing ugly shoes.

As Miuccia Prada knows, there's ugly, and then there's ugly-chic. Prada's based her whole career around that concept–and the recent focus on her life and career, courtesy of the Met's exhibit last year, might also have contributed to this trend. "We may also still just be on the heels of last year's ugly chic Schiaparelli exhibit at The Met," says Medine.

But Medine has another theory, too. "If you want to bracket this trend into the genre of Things We Miss About The '90s, then it's totally possible that this is a nostalgia thing," she says. "Travis Birkenstock, summer camp-fostered Adidas slip on wearing and the embarrassing old family photos of hikes through Israel in which every member wears a matching pair of Tevas. Yes–it's probably totally an irony thing."

I think she hit the nail on the head. It reminded me of the inspiration behind Misha Nonoo's Adidas-filled resort collection: The designer's own prep-school uniform, and its various iterations throughout the day (clunky sneakers for gym class, Adidas shower shoes for the shower).

"We are the generation of the '90s and I think we have those moments resonating in our mind," says Distenfeld. "We are looking at a time of pure minimalism and simplicity and seeing how we can take that past and make it present."

Nostalgia plays a part for sure, but I think it's mostly, as Medine says, "an irony thing." There's something subversive about all the "cool people" wearing dorky shoes. It takes balls. You have to admit, that after several critically-acclaimed, distinctly minimalist collections, Philo's spring 2013 shoes were almost an affront. It kind of made you wonder, is she just fucking with us?

But no, Philo was just tapping into a bigger trend–a trend that, if the Resort 2014 collections are anything to go by, has legs. Click through the gallery below to start stocking up.

More from Fashionista:
Jean Paul Gaultier Strikes Back at Tim Blanks Over Bad Review
It's Happening: Kanye West for A.P.C.
Ugly Is In for Summer Footwear
We Tried a Bunch of At-Home Hair Removal Products So You Don't Have To