For the Costume Institute Gala, Banks rocked an edgy low ponytail. "I wanted her hair to mimic the flirtation and texture of her dress," said Frederic Fekkai stylist Adir Abergel, who worked with the star. To keep the ponytail from feeling too gym-ready, Abergel had a little trick: He skipped elastics and turned to bobby pins instead. "I wanted the hair to hug the nape of the neck. If I had used a rubber band, it would have lifted the ponytail up and away from her neck too much," he explained.