I was taught undergraduate discrete math by Dr. László Székely, who taught it in a very dry, robotic way; he may as well have been reciting a graduate-level textbook. As far as I remember, he told about two jokes the entire semester. One of them was my favorite moment in that class, but nobody else seemed to think it was funny, or even recognize it as a joke.
He was working with a particular limit, and apparently the relevant behavior we were looking for was whether or not it converged to zero as it approached infinity. He showed with some algebra or something that the function was simply the constant one, “…and one does not go to zero as far as we know.”