Say what you will about Jimmy Fallon—his schticks are repetitive, he's an adult child—but there are human emotions underlying that cynical viral video factory. Fallon cries at the things that make other humans cry, including the death of Robin Williams, "the Muhammad Ali of comedy."

As evidence that Williams was one of the quickest-thinking comedians working, always 10 steps ahead, a tearful Fallon presented Williams' first-ever appearance on Johnny Carson's Tonight Show.

Here's a bit more from that 1981 appearance, where Williams' manic versatility and ability to switch characters instantly were on full display:

[H/T Digg]