There is all sorts of subtle humor, such as in I, when Michael explains to Kay how "Luca Brasi held a gun to his head and my father calmly explained that either his brains or his signature would appear on that piece of paper." The look Kay gives him back is priceless.
Yes! That's my favorite humorous part as well. The way her expression changes is fascinating.
But if Clemenza can figure a way to have a weapon planted there for me then I'll kill 'em both.
