Mikhail Baryshnikov is the most famous living ballet dancer in the world. He defected to Canada in the mid-1970s. In the ballet world, he’s worked with everyone from George Balanchine to Alvin Ailey to Twyla Tharp. He’s gone on to become an Oscar and Tony-nominated actor, and now he’s starring in a show called “Man in a Case” that opens at The Broad Stage in Santa Monica tonight.