I had the pleasure working with him a number times over the years, and had great respect for his intellect and professionalism, and still do.
However two? nights ago I saw him on a rerun of his standup on Johnny Carson from decades back, and likely maybe one of his first Carson appearances, not sure.
I was shocked at how lame his performance was, it was almost depressing, although you could see glimmers of his future excellence and wit.
If you are a Carlin fan, I suggest, don't watch it if given the chance.
edit I found the video, its 1981, so far from his first Carson appearance, view at your own discretion.
https://www.youtube.com/watch?v=3jus-OaJV8E