Discovering that the gift-distributing Elfix aliens have disappeared as the Night of Dancing Stars approaches, Geronimo Stiltonix and his spacemice crewmates race to find the missing aliens before the celebration is ruined.

"Professor Greenfur, the onboard scientist on spaceship MouseStar 1, has changed color from green to--orange! What's going on? To find out, the spacemice travel to his home planet of Photosyntheson. There, they learn that all of Professor Greenfur's relatives are being threatened by the nibblix, tiny aliens with very sharp teeth! Can the spacemice help in time?" --

While at the beach, Geronimo Stiltonix stumbles upon a mysterious treasure map. The spacemice follow it and end up on Aquarix, a planet that's entirely underwater. During their exploration, they face fur-eating seaweed, ferocious piranha aliens, and...pirate spacecats! Can the spacemice keep the spacecats from stealing the treasure?

Traveling to the planet Jurassix to warn its inhabitants of an imminent comet strike, Geronimo Stilton and his crew encounter ferocious, dinosaur-like beasts who have an appetite for rodents.

Geronimo Stiltonix and his spacemice crewmates travel to a planet where delicious mozzarella grows in order to restore harmony between its alien inhabitants and the cheese-loving slurp monster.