The Green Moon is a moon, presumably in the Solar System.
The Green Moon is similar in appearance to the Moon, but green. It may be made of cheese, although the cheese may only be contained inside of it, as it can be seen inside craters on the moon's surface. The Green Moon is inhabited by at least one, and perhaps several, small green aliens. One in particular stands out: The Angry Cheese Alien, who, upon witnessing the arrival of a visitor from the planet Barks, threw a glob of cheese in it's face.
Behind the scenes
The Green Moon first appeared in 1965 in Astro Pooch.