You may have noticed that animals have a sense of fun, but not a sense of humor.  James V. Schall, S.J., explains why:

“Humor arises because we are rational beings who can and do delight in the things that we know, in the things of the mind.  We are amused in the comparisons we make, either in speech or in reality, between what we expect and what is said or what happens.  The correction of mind by mind is one of the greatest of human enterprises.  We do not want, as Plato said, a lie in our souls about the things that are.  In things of the intellect too, a brother is helped by a brother.  Indeed, this correction is one of the great divine enterprises.  God, in revelation, undertook to do so Himself.”

(The image is from the famous 1957 spaghetti hoax.)