“Havaianas were almost synonymous with poverty,” said Porto. “They were sold like a commodity, with no investment in design or marketing or innovation, and the whole business model hinged upon selling increasing numbers of pairs in order to drive production costs down.”

By the early 1990s, with domestic competitors beginning to eat away at Havaianas’ market share, label executives made a bold, 180-degree shift in strategy. Their plan, aimed at rebranding Havaianas as a fashion accessory, would prove so wildly successful that it has since become a business school case study in marketing.

The label looked to inventive wearers who had long been transforming their bicolor sandals into single color ones by flipping the white-topped sole over. In 1994, Havaianas introduced a new line of one-shade sandals in black, royal blue, pink and purple.

Suddenly, middle- and upper-class Brazilians who either wouldn’t have been caught dead in Havaianas or donned them exclusively for the short trek from their beachfront apartments to the sand, were snatching them up in multiple shades for all occasions.

Ladies who lunch from Rio’s tony Leblon neighborhood wear them to all-important visits to the hairdresser or even out on dates. Private school scions use them to mark the goal box during beach soccer matches. Moneyed businessmen wear them while walking the dog or out to a high-end “churrascaria” barbecue.

Havaianas now come in an ever-changing rainbow of 23 shades, some emblazoned with eye-popping prints on the soles or rubber appliques on the straps. At the brand’s concept store on Rua Oscar Freire, Sao Paulo’s answer to 5th Avenue in New York, Havaianas devotees can get bespoke sandals made to their color specifications or emblazoned with their initials.

Swanky Brazilian jewelry label H. Stern has crafted a limited edition of six pairs bedazzled with diamonds and glinting with gold. Designer Gustavo Lins, a Brazilian who’s among the elite cadre of Paris’ haute couture purveyors, sent out a collection of made-to-measure garments paired with Havaianas. The brand has also collaborated with Missoni to create a line of flip-flops emblazoned with the Milan-based luxury label’s hallmark zigzags.

While prices for the basic, no-frills models have remained low, retailing in Brazil for just $5, a premium off-the-shelf pair goes for up to $28 here. In the U.S. most models are in the $20-$30 range.

Brazilian-born former model and socialite Andrea Dellal keeps her dazzling Rio apartment stocked with Havaianas in every conceivable size and color.

“I keep baskets full of them in all the bedrooms, and my guests and my children and their friends help themselves,” said Dellal.

She said she had vivid memories of wearing Havaianas to the beach as a child. Now she wears them everywhere.

“I wear them with my Dolce & Gabbana dresses during the day because they’re easy to run around in and sometimes I wear them at night with long dresses. I love the look,” said Dellal, whose other footwear of choice includes vertiginous heels by Manolo Blahnik and daughter Charlotte, who’s behind the high-end London shoe label Charlotte Olympia.

Still, despite, or perhaps because of, their adoption by the elite, Havaianas continue to appeal to their original customers at the bottom of Brazil’s class hierarchy.

“The popular classes are buying more Havaianas than ever,” said consultant Porto. “Poor people have the right to be fashionable too, and people in this group tend to save up for different models and lots of colors.

“They see their bosses wearing Havaianas, they see TV stars wearing them and even foreign movie stars in them, and they feel proud to wear them.”

A single factory in the northeastern state of Paraiba churns out all those flip-flops, but a new site is under construction in central Minas Gerais state to keep up with demand.

The brand is looking to grow in other emerging countries, such as China and India, but its core will remain unapologetically Brazilian, Porto said.

For working-class Brazilians, who were the reason for the brand’s initial success, anything less would be unthinkable.

“I have been wearing Havaianas ever since I can remember,” said Vania Lucia Ribeiro, a 32-year-old maid who lives in a distant Rio de Janeiro suburb. “I buy them for my children and I buy them for myself. I can’t imagine living without them.”