Robin Williams (who attended Juilliard on a full scholarship) was performing on the streets of New York City in the late 1970s, during the same time he was appearing on Mork & Mindy. Last year someone Tweeted the below photo from 1979, explaining: "My aunt took this picture of Robin Williams in 1979 street performing in NYC. Who would have guessed." Williams Tweeted back, "Thanks for the photo!"
— Ryan Haught (@thathaughtguy) December 20, 2013
Two years prior to this photo being taken, Williams was dubbed one of the "hottest young stars." He was skyrocketing to superstardom, frequenting Studio 54, and avoiding the press—turning down requests for interviews, photos, and filming of his act.
The NY Times raved about Williams after his Copacabana show in 1979, also noting that he was "nice... seems to beam with sweet, uncomplicated pride."
Here's a 1983 stand-up set from The Comic Strip on 2nd Avenue:
In the 1980s he hosted Saturday Night Live a few times, and made some short cameos as well. He hosted February 11th, 1984, November 22nd, 1986, and January 23rd, 1988. Sadly, SNL makes it pretty hard to revisit any of these (they've taken down all their YouTube videos). You can watch Williams's monologue from 1988 right here.
From the Met Opera House in 1986:
Here's one of his many appearances on Letterman, in 1991:
Williams appeared on Sesame Street a number of times, and below you can see some of the segments from over the years. Yesterday, Sesame Street tweeted, "We mourn the loss of our friend Robin Williams, who always made us laugh and smile."
From his Live on Broadway DVD from 2002, here's Williams talking about a hot day in NYC:
And here's Williams's terrific appearance on Louie: