“Supers, as they are commonly known, stand on their feet for hours on end but only rarely get to take a bow. They nod and smile imperceptibly after a ballerina like Michele Wiles whips off rounds of triple fouette turns in “Swan Lake” but are forbidden to applaud. Being a courtier in “Raymonda” or a gritty butcher in “Romeo and Juliet,” is a thankless job. But in a full-length story ballet, someone has to blend into the crowd. Apart from having a love of dance and strong legs, supers, who generally are decades older than the dancers with whom they share the stage, must also be reliable.”