International girl group Katseye danced to the song "Milkshake" in a viral Gap ad. (Gap/YouTube)A 90-second video starring a handful of beautiful, distinct-looking women in jeans broke the internet, and for once, it wasn't because of outrage. The Gap ad, which featured the international girl group Katseye performing sharp choreography to Kelis's nostalgia-inducing 2003 song "Milkshake," was one of the better-timed ads in history.