Tonight’s guest: John Lithgow, whose new film is Love Is Strange, and who’s done double duty on the Broadway stage, having just played King Lear in Central Park, and preparing to play Tobias in A Delicate Balance, which begins previews next month. Colbert’s best guests are the ones who get, and can react to and keep up with, his sense of humor. That makes Lithgow an ideal guest, so stay tuned.