Even a world-class ballet company needs dancers it can count on to never come down with the flu. The problem is, they dance sensibly too. Or that’s what we assumed. At the New York City Ballet, Megan Fairchild was cast in so many grueling neoclassical roles—in which the feet do variations on twittering for longer than seems possible—that we came to think of her as “useful.” But the ballerina turned out to possess a particularity that stretched beyond type. In Balanchine’s Divertimento from ”Le Baiser de la Fée,” she cast her spell as an elusive fée not by being the ballet equivalent of a manic pixie dream girl but from a self-reliance so entire that it shaded into unknowability. She didn’t need her cavalier, and she didn’t need us, though she would grace us with her presence for a time. Twenty-five years, to be precise. Fairchild’s farewell performance takes place on Sunday afternoon, May 24. For her send-off, she will dance the titular role in Coppélia—a young woman playing a doll playing a young woman, who emerges from the disguise more real than ever. And she has. —Apollinaire Scherr