The one notable contribution of human culture to the galactic culture is the art form known as slapstick humor. The most well-known practitioner of this art form is a long-dead Human known as Jerry Lewis, who is revered throughout the galaxy. (Oddly, he is far less respected on the Human homeworld.) Since all Humans look alike to members of every other species, non-Humans have a hard time not associating every Human with the slapstick antics of Jerry Lewis.
