Came across this while flipping through the ‘humor’ section on Flipboard yesterday … it looks kind of Saturday Night Liveish, but probably isn’t. The source (quickdrawartist) suggested maybe the Tonight Show:
Death of Socrates ~ Steve Martin Style
quidquid bene dictum est ab ullo, meum est
rogueclassicism 
I went to a paper on this sketch once – it was a while ago so I can’t remember where it was from, but I think it might have been Saturday Night Live…
At the very end, that looks like David Letterman standing up to applaud.
No, this isn’t from any of the Late-Night Shows. As a rising comic, Steve Martin was actually given a number of different shows, self-contained Comedy Specials, that ran on prime time network t.v. (I think it was NBC). This is from about ’77, or 78, I believe.
Thank you, rougeclassicist for the video. It made me laugh.