While Garfield waits for Jon to get more lasagna on his birthday, he is observed by aliens that resemble lasagna.
On Garfield's birthday, Jon sleeps until Garfield wakes him using an alarm clock. Jon cooks him 8 birthday lasagnas, but Garfield angrily notices that Jon is 1 lasagna short. He goes upstairs where Jon is editing a video on his computer. Soon, Jon notices and goes to the market so Garfield takes a nap, while Odie runs around obliviously.
Meanwhile, a spaceship launches outside their house and returns to an space station that resembles an oven, close to the sun. A lasagna named Ricotta goes to the leader of the space lasagna, who shows him pictures of Garfield holding lasagna and tells him to go and see happened to them. So Ricotta goes back to Earth where he sees Odie chasing a beach ball. He measures Odie's brain power (which is shown to be zero). As he does, Odie's ball pops. Ricotta then picks a flower, uses it to sneak past Odie, and enters Jon's house.
Garfield is still asleep, so Ricotta uses a ketchup bottle to take a ride on a garbage can. When he falls in, he tips it over, waking Garfield. Ricotta stays on a plate and thinks he's okay until Garfield notices him, thinking he's the last lasagna. He is about to eat him when Ricotta begs him not to eat him. After that, he beats Garfield up and runs away. When Garfield looks out the pet door, Odie runs into him before Garfield tells him what happened. Odie, however, doesn't believe him. Odie picks up a scent and follows it to a bush. There, the latter finds Ricotta talking to his leader.
Meanwhile, Garfield is worrying when Odie runs into him again. Garfield flies out of his bed and returns with a garbage can on his head. Odie pushes him to a window where Garfield doesn't see anything. Suddenly,the two see a spaceship full of space lasagna. The lasagna come out with the leader and Ricotta. So Garfield hides in the garage. The lasagna come in, chase Odie and tie him up. They look all over the house for Garfield. At last, they come in Jon's room.
They see videos of Garfield eating lasagna and become scared of him. Garfield comes out of the garage, unties Odie, and goes to Jon's room. When they see him, they all run out of Jon's house and return to space. Soon, Jon returns with a birthday lasagna, but Garfield and Odie scream and run away. Meanwhile, the lasagna go back to their planet screaming.