Shortly after Natalie left, Rooney Mara and Michael Fassbender came to the set to shoot their scene, where they can be seen hugging it out.
So there's Portman with her balloon-like ass cheeks being hugged by her pants and wedged in her can't-miss-it thong, with the next shots showing her in a dressing room with show girls - all have their asses on display in thongs, and all have butts that are depressingly flat.