Casper emerges from a subway station, following a crowd of scared strangers. He encounters a man saying "see the wonders of the moon for ten cents," and offering a sight through a telescope. Casper scares the man away, then uses the telescope to see the moon. He then flies to the moon for a visit. Casper lands on the moon, disappointed to find no man on the moon. He lies down to nap, then tiny moon men emerge from holes. They capture Casper, like Lilliputians did to Gulliver, then place him in a cage on wheels, in which they tow him to the Ruler of the Moon, King Luna. The King addresses Casper as a monster, and treats him as an enemy. Casper playfully picks up King Luna, and the king has him placed in the royal dungeon. A dejected Casper is imprisoned. Then animated trees attack the city of the moon men. The moon men defend their fortified city with flaming missiles. The tree monsters fight back with water, then break through the town walls. When the fight seems lost to the tree monsters, Casper escapes his cage, and helps the moon men. Casper goes underground. The friendly ghost then pulls trees' parts through the moon surface and ties them together, immobilizing the trees. The frustrated trees writhe and strain against the knots Casper has tied. Casper and the moon men have won. Then, and only then, does King Luna embrace Casper as a friend. King Luna knights Casper for the valiant defense of his people. Then all the moon men join in singing the Casper theme song.