This is a clip from a long out-of-print documentary called The Masters Of Comic Book Art. It's introduced by Harlan Ellison.
Jack Kirby is seen talking about his cosmic Marvel comics (Galactus, Silver Surfer etc.) and how those led to his Fourth World books at DC. He then says a few words about the history of comics.
I never met Jack Kirby, so I don't know if he was always like this, but he has a strange mixture of emotions as he talks: angry and serious but somehow always on the cusp of smiling, too. A fascinating man and an incredible talent.