Robin Williams was a great comedian, whose greatest strengths lay in ad-libbing. It is said that the writers for Mork and Mindy left intentional gaps in the script so that Robin could fill it in with his lightning-fast ad-libbing.
He played very funny characters on stage and TV, but he also played very warm, but serious characters on film. One serious character was his role as counselor Sean Maguire in the 1997 movie Good Will Hunting, a film loosely based on the life of Will Sidis, a real-life savant, rumored to have an IQ of 250 to 300, but his IQ could not have been as high as that. Indeed, the scale does not go above 200.
Whatever he played, there was an undeniably human quality about every character he played, as far as I could tell. Even the zaniest or improbable characters had a human quality you could connect with emotionally.
He was an actor with an amazing amount of energy, and he will surely be missed.
Robin Williams died today at age 63.