Jerry is confronted by a library detective over a book he didn't return to the library 20 years before. Mr. Bookman is played by Philip Baker Hall. You have to wonder how many times they had to do this skit since you know Jerry kept breaking up. He still can't keep a straight face in this take, but it was probably the best one they could do.
If you are young or from a different culture, this is hilarious because Mr. Bookman is doing a parody of Joe Friday's lectures in the old cop-centric series Dragnet. (via reddit)