Garfield accidentally journeys to various alien worlds when he winds up in an extraterrestrial vehicle.
Jon drives to the market with Garfield and Odie. During the ride, Jon notices the clear night sky and wonders about other beings beyond their world and time. Meanwhile, an alien travels back home, with his wife Miriam demanding that he get cheese puffs and a jelly donut. He proceeds to do so by stopping at Earth in the 21st century, parking right next to Jon’s car after Jon goes into the store while Garfield sleeps in the car.
Garfield soon wakes up to the presence of a spider, which he tries to swat. When he attempts to do so at the front of the car, he makes the lid flip open, bringing him into the alien’s vehicle and inadvertently activating it. It takes him away from Earth and to a planet made of cheese. There, he encounters who he thinks is Squeak, but turns out to be a savage alien resembling a mouse, who is soon joined by others in chasing him. Garfield then requests dinner, only to be made dinner by becoming part of a sandwich. He soon escapes and returns to the alien’s vehicle and manages to escape from the planet.
In space, he consults a book to find out how to fly the vehicle, but has no luck. He is eventually taken to a planet which has a creature that looks (and acts) just like him. However, the creature is also able to occasionally turn into a monster, which he does right then. Terrified, Garfield retreats to the alien’s vehicle, which takes him through a wormhole and to a planet that appears to be his own. However, he then finds out that the planet’s citizens consist of giant spiders, two of which are Jon and Odie. Finding the tables turned, Garfield runs away from the spiders as they prepare to swat him.
Back on Earth, Jon and Odie discover Garfield missing. They get help from the alien traveler, who notices that his vehicle is gone as well. The alien uses a remote homing device to recall his vehicle. As Garfield tries to get back to the vehicle, he sees it getting ready to depart. He manages to grab on to the back of it as it leaves the spider world and returns to Earth. With both back, the alien leaves for home, only to briefly return to get the jelly donut. Garfield notices a spider on the ground and flees in terror.