“I can’t believe that he’s here now, I can’t believe I know Groucho Marx, I can’t believe that there is a Groucho Marx,” a young and sparkling Dick Cavett said in 1968 when introducing his comedic idol on an early iteration of Cavett’s legendary talk show.
And though I’ve known Cavett since 1979 when I began work as a production assistant on his PBS series, I confess that I feel almost the way when...