Whether it's the withering economy or the perceived cost-effectiveness of creating an experiential environment that lasts more than one night, pop-ups are an enduring favorite among marketers in New York. Also growing in popularity are in-store events and close partnerships—not sponsorships—between brands. Illustrating these trends is the Gap and Havaianas Urban Beach Flip-Flop Shop, a joint effort between the two fashion companies inside Gap's Fifth Avenue flagship. The pop-up opened to the public today and runs through Sunday, June 13.

Although Havaianas has made several appearances at New York Fashion Week, this is the first freestanding marketing endeavor for the Brazilian flip-flop maker, but one that the company thought would do better with the aid of an established retailer. "We did think about doing the pop-up on our own, but why wouldn't we go out and collaborate with a premier vertical retailer and see the success rate we could have?" said Elaine Sugimura, president of Havaianas U.S.A. "The power of both brands we felt would be greater than doing this on our own and having to manage this ourselves. This year we felt that this would be a great learning experience for us and a great partner to do it with in the Gap."

The temporary store isn't just a good fit for Havaianas, it's also something that matches Gap's current marketing concepts. The location is a small annex inside the 54th Street and Fifth Avenue space, which Gap has been using for different promotions since 2008. "It does feel like its own unique space, but it's right adjacent to the store," said Kim Terry, Gap's senior manager of engagement marketing and PR. "We've done a couple different things with that space, starting with the partnership we did with Collette, and we've really created a rotating pop-up store. So we've brought in partners and concepts and ideas into the space since fall of last year."

While the pop-up sells flip-flops and offers a station where consumers can customize them, it also has a selection of Gap's summer clothing collection for purchase. "If you look at Gap's advertising scheme this year, it's all about color, and it's all about the solid color. When you look at the flip-flops we have in there, Havaianas is very much in alignment with that," explained Sugimura. "I think it's taking the essence of both brands and capitalizing on those essences. The essence for us is fun; it's about joy; it's about the unexpected. And the unexpected for us, I think in some ways this year, is that we're at the Gap."