Robin Williams, born in Chicago on July 21, 1951, studied theater at Juilliard School before taking his stand up act to nightclubs. He was cast as Mork, an alien visitor to Earth, for a 1974 episode of television’s “Happy Days.”

“Happy Days” star Henry Winkler said it was “unimaginable that this is the reality today, that this incredible human being, incredible, delicate, funny, dramatic human being is gone.”

Winkler said he “realized I was in the presence of greatness” at Williams’ first rehearsal as Mork.

“I just realized my only job is to keep a straight face,” said Winkler, who played “The Fonz.” “And it was impossible. Because no matter what you said to him, no matter what line you gave to him, he took it in, processed it, and then it flew out of his mouth, never the same way twice. And it was incredibly funny every time.”

The role led to the spin-off show “Mork & Mindy,” which showcased Williams’ usual comic improvisation talents.

He proved his dramatic acting skills in “Good Will Hunting,” a 1997 film that earned him a best supporting actor Oscar.

His memorable movies over the past three decades includes “Good Morning, Vietnam,” “Dead Poets Society,” “Mrs. Doubtfire” and “The Birdcage.” The list is much longer.

Williams credited the influence of Jonathan Winters’ comic irreverence and quirky characters as a great influence on his comedy. The connection between the two was completed when Winters was cast as Williams’ son on “Mork & Mindy.”

When Winters died in 2013, Williams said he was “my idol, then he was my mentor and amazing friend.” He tweeted that Winters was his “Comedy Buddha.”

“Mork & Mindy” co-star Pam Dawber simply said “I am completely and totally devastated. What more can be said?”

WIlliams and Dawber reunited on TV earlier this year on an episode of the CBS comedy “The Crazy Ones.”

Williams’ fans can look forward to four more movie appearances coming to theaters, including another installment in the “Night at the Museum” franchise.

The film, set for a December release, has Williams reprising the Teddy Roosevelt role he delivered in the first two comedies.