American Ballet Theatre holds a reunion of dancers. “To see them was to see the company’s long history, from 91-year-old Annabelle Lyon, who danced with Ballet Theater from 1940 to 1943 and was the company’s first Giselle, to Jamar M. Goodman (1998 to 2003), who, after Ballet Theater’s performance of “The Dream,” was besieged backstage at the Metropolitan Opera House by women in full fairy regalia eager for hugs and the latest news.”