While collecting rocks, Goby meets two astronomers who are looking at the Moon, he then hopes he can get a Moon rock. The Guppies then go to the planetarium where Goby is in for a big surprise from Mr. Grouper.
The opening begins as Molly tries to say "it's time for Bubble Guppies" However, Gil interrupts by singing "Twinkle Twinkle Little Star" while looking for stars with his telescope. Then Molly asked him to look down and the stars exclaim "It's time for Bubble Guppies".
Goby is on his way to school when he suddenly sees an interesting rock to add to his rock collection. He then runs into a couple of scientist observing the moon. They begin to talk to Goby about the moon, which makes him begin to question what sort of rocks are on the moon and in space. He then heads to school but forgets his rock collection! Luckily, the scientist inform him of it.
Reaching school, Goby tells everyone what happened and they begin to discuss Space. They then begin to sing "Sun, Beautiful Sun".
After the song, Gil and Nonny go to the moon Pizzaria, owned by Molly. They order one pizza, but find it difficult trying to share the pizza so that they both get an equal amount. But soon they manage to figure out how they can share it as Mr. Grouper announces "it's time for lunch!".
After Lunchtime, Molly describes that the moon is round, just like a Pizza. When Gil's pizza arrives he looks at the stars, which then hop down and try to chase him for said pizza!
In class, Mr. Grouper, Deema, and Gil are playing solar system. Which makes the entire class begin to wonder about the solar system . Then Deema sings orbit
Oona and Deema pretend to be aliens on outer space looking for a place to take a nap but a giant space monster keeps following them! They try to hide on Mercury, but its too hot and they try Neptune, but its too scold. After they leave Neptune, they come across Earth, which is just right! The monster arrives again but Deema, being in no mood asks him what the problem is. He reveals that he was sleepy too and had wished to nap with them in the perfect spot. So they all sleep together as the story ends...
Molly begins to describe the many planets in the solar system. Gil interrupts, wanting to show the biggest planet. He tries Mercury, then Mars but neither are the biggest. Upon asking Molly, who informs him its actually Jupiter, the giant planet shows up and tries to chase Gil!
The guppies went to the planetarium, where Goby met the scientist earlier. In the planetarium, they take a trip to the solar system while singing and observing everything around them. When they get lost, they return back to Earth and exit the planetarium. Goby notices that an odd rock has been added to his collection but he doesn't know who could have put it there!
Molly mentions that a lot of things are in the Solar System as Gil approaches, dressed as an Alien. She asks him where he is from and when Gil replies, "Jupiter", the giant planet returns and tries to chase him again!