Robin Williams is a stand-up comedian and actor who first came to national attention in Mork and Mindy. His breakthrough role was as a hip, wisecracking, anti-establishment DJ in "Good Morning, Vietnam. He has frequently portrayed doctors or therapists; in Good Will Hunting he played a professor of psychology treating an underachieving genius (Matt Damon).
In a couple of movies he plays a character who becomes popular due to a fraud. In the first, he's elected president when a computer program gives the wrong election result. In "World's Greatest Dad" his character provides the fraud when he palms off his own writing as that of his dead son.
Many of his movies deal with death. He played an Alaskan murderer; a pediatrician who dies in a car accident (and then his wife commits suicide) in "What Dreams May Come".