Robin Williams was a madcap genius in performances of all types of entertainment, from stand-up to feature films. Known initially as a comedian, he surprised with his ability to play serious dramatic roles. His breakthrough came in the 1970s TV comedy Mork and Mindy; as the alien Mork, much of Williams’s dialogue was improvised, as would be the case in most of his comedic roles. Once established, Williams worked tirelessly in show business, going on to appear in many feature films, including Good Morning, Vietnam (1987), Dead Poets Society (1989), and Mrs. Doubtfire (1993); he won an Oscar for his role as the psychologist in Good Will Hunting (1997). He also did voiceover work in animated films and returned to television with The Crazy Ones (2013). Williams battle substance abuse for years; he made serious fun of his struggle in his comedic monologues.