In film and television, it’s common to see characters at various ages and stages of their lives, portrayed by different actors—but, in the vein of Barry Jenkin’s Moonlight, it’s much less common to see multiple iterations of a character, each as fully realized as the next. Such is certainly the case with National Geographic’s Genius—executive produced by Ron Howard and Brian Grazer of Imagine Entertainment—in which Johnny Flynn and Geoffrey Rush are two equally brilliant…