American Idol
Credit: Michael Becker / FOX (2)

American Idol history was made last night when Haley Reinhart (at left in Domino jeans, a Meghan top, House of Harlow boots and Sisco & Berluti bangles) became the first contestant ever to sing an unreleased song—Lady Gaga's "You and I." Lauren Alaina (at right in a Sheri Bodell chain dress, David Lerner leggings, and a Bebe belt) channeled her inner Carrie Underwood during a rendition of "Flat on the Floor," before the cast changed gears to perform hits from the '60s and '70s. "Every week I am pushing their style more and more, but the era had nothing to do with it. I want them to be themselves week after week," the show's costume designer Soyon An told InStyle. "It's all about choosing looks that fit and enhance their individual style." Click through the gallery for more designer details from last night's episode!