Two weeks ago in Soho, about 300 people showed up at the Spanish clothing store Desigual sporting only their skivvies. No, it wasn’t the latest fashion look for fall, but a response to the store’s offer that the first 100 people in line, wearing only their underwear, would get free outfits, and the rest a 50 percent discount on clothes purchased that day. There was no shortage of onlookers and tour buses were stopping to let tourists take photos of the risqué retail scene.