The theme for last night's Costume Institute gala was challenging: superheroes. Oddly enough, it turned out to be the one time when nobody wore their underwear outside their pants, but stars were inspired to experiment — with very varied results. Our favorites? Zac Posen and Kate Mara's cartoon primary colors, Christina Ricci's rose tones, and Anna Wintour's alien queen look. But who forgot to tell Mary-Kate Olsen that Phyllis Diller isn't a superhero? To see 56 looks from last night's red carpet, click on the Party Lines slideshow. We've got red-carpet video of Coco Rocha, Fergie, Jessica Stam and the original Wonder Woman, Lynda Carter, too.