The off-Broadway comedy Viagara Falls begins with a recording of Frank Sinatra crooning “High Hopes,” an appropriate theme song for a show about two elderly men plotting a night of passion fueled by some little blue pills. The three-person play, starring co-author Lou Cutell and Love Boat vet Bernie Kopell as lifelong friends and Teresa Ganzel as the sweet-natured prostitute they hire, opens on July 21 at the Little Shubert Theatre. After a preview matinee, the stars and director Don Crichton chatted with Broadway.com about their own high hopes for the show.