It is a song that expresses what Casey is feeling about his life and his career and his choices. It is the root of fun for this odd show, a comedy that keeps us amused for two hours. It is time to laugh, and heartily at that, for the show gives us every chance from moment to moment. Michael Wartella does a superb, professional job playing the straight man whose career takes an odd, unanticipated turn. “The Legend of Georgia McBride” plays at the Colonial Theatre, 111 South Street, Pittsfield, MA, through August 16.