There's a saying about the weather in New England - if you don't like it, just wait a few minutes. YouTube's like that; if they don't have a clip, just have patience, it'll be along.
That's been the case for me in my search for Mike Nichols and Elaine May videos. They came from the original Second City lineup in the '50s, and their sharpness and wit in their improvisations was absolutely unmatched. Periodically I'd look for something of theirs; when I couldn't find it, I'd remind myself: patience.
Now there's a fresh batch of some of their best on YouTube; this is my favorite, but I recommend checking the others if you have the time.
A mother reduces her rocket scientist son to an infantile state in six and a half minutes. This sketch was born when Nichols's own mother actually used the opening line that May uses here. Barely dated after almost fifty years (even the phones are cordless), this has a wicked incisiveness you just can't find anymore.