It was a big week for your phone, from fashionable Bitmoji outfits and new emojis to a new feature from Instagram called Boomerang. The standalone app takes a burst of photos and stitches them together into a mini video that plays forward and back—a lot like a GIF. In short: endless fun. Below, models like Karlie Kloss, and Cara Delevingne, and Lucky Blue Smith as well as Kim Kardashian, Kendall and Kylie Jenner show how it’s done at Olivier Rousteing's birthday party.