Kid to daddy: "Why do they call it Uranus?"
Daddy to kid: "Cause, son, it's Uranus."
Listen up, nimrod! The joke is that the kid asks why the planet is called "Uranus." The dad responds, "Cause, son, it's Uranus." The humor comes from the fact that "Uranus" sounds like "your anus." You probably still don't get it, you troglodyte.