Ann Roth began with a few instructions: “Do NOT call me amazing. Do NOT call me a 91-year-old legend. Do NOT call me the oldest person in the Barbie movie.”

I had driven four hours through a biblical downpour to interview the revered costume designer. After a hike down a dark path through the woods to an 18th-century house in Bangor, Pennsylvania, I felt as if I were opening the Narnia wardrobe and entering a whimsical fantasy world. Owls perched on rafters. Angels from Naples, Italy, dangled from the bedroom ceiling and chandeliers. A stone mantel was lined with miniature animals amid Oscars, Tonys and BAFTAs.