Robin Williams first appearance on the Tonight Show with Johnny Carson:
http://www.youtube.com/watch?v=Qr1DSLoHni0
Robin Williams with Jonathan Winters and Johnny Carson:
http://www.youtube.com/watch?v=_NqEKvk9F4I
Robin Williams discusses Awakenings with Johnny Carson:
http://www.youtube.com/watch?v=iqdSagycCWc
With Craig Ferguson 2010:
http://www.youtube.com/watch?v=CKAcV0YF9o4
With Conan:
https://www.youtube.com/watch?v=6wCqG-Sa-Vc
With Craig Ferguson 2013:
http://www.youtube.com/watch?v=Yw9Evwb1vtQ
bump for later.
Personally I thought Williams unscripted moments were silly and characteristically juvenile.