Garfield the Cat is walking home from Vito's Pizzeria. He then spots something falling out of the sky. It crashes into a nearby warehouse, and Garfield goes running toward it. Upon arrival, he finds the wreckage of an alien ship in the warehouse, and finds all the warehouse workers with scorpion-like creatures wrapped around their faces. The creatures loosen their grip, and small serpent-like creatures emerge from the chests of the workers. Garfield then takes off running before the creatures can notice him.
He comes home and finds Jon Arbuckle and Odie the Dog asleep on the floor. He tries to warn them of the creatures, but they don't wake up. He throws a bucket of water at them, getting their attention. He then explains everything after the situation cools down. Jon and Odie proceed to hide under the dinner table, with Garfield facepalming at their cowardice. He then proceeds to barricade all the exits and grab a butcher knife from the kitchen. Just then, a knock is heard on the front door. Garfield tiptoes toward the door and opens it partway and sees the Powerpuff Girls.
They ask him if he saw "a guy with Jamaican dreadlocks and a mask" go through. He says he hasn't, and lets the girls in. Once they get in, he quickly shuts the door and locks it. He then tells them that he did see creatures at the warehouse.
Just then, a scratching sound is heard coming from the kitchen, and Garfield and the girls walk in, and the silhouette of a humanoid figure with a long head, a tail, and tubes coming out of it's back is seen. The girls then get into a battle pose and call out to the creature. Garfield goes upstairs to look for more of the creatures. He then hears a scream and sees the mailman being assaulted by one of the creatures.
"Oh god, oh my god" Garfield says. He then stumbles back and falls down the stairs and gets up dazed. He then hears a searing sound coming from the front door. He looks over and sees the door melting away.
Then one of the creatures enters the house, followed by three others. The girls fight the creatures off, and Garfield stabs one in the head with the knife and runs away screaming. Jon and Odie then look up and see two of the creatures standing overtop of them. They run away screaming as the creatures pin them to the ground as more of the scorpion-like creatures wrap themselves around their faces.
After a minute or so, the creatures detach themselves from Jon and Odie's faces, then a serpent-like creature emerges from Jon's chest, and another one, this one with limbs, and in a quadrupedal stance, emerges from Odie's chest.
Garfield and the girls flee the house, and are cornered by a tall humanoid figure with dreadlocks, a mask, and with a shoulder cannon, and small skulls formed into a necklace, who unsheathes wrist blades and points them in the girls' direction. Just then, a random hobo comes running at the figure with a pipe, only to be knocked over with ease, and his head is ripped from his body, with the spine attached. Garfield and the girls then proceed to run, with the figure chasing after them.
They then end up cornered in the alleyway near the deli, and some of the other creatures come out of the shadows and battle the masked figure. The creatures are easily bested by the masked figure and decapitated, with some of their blood hitting Garfield's hand, and some of the skin on his hand burns away, but he shakes his hand before the bone can burn away.
Garfield and the girls then head toward the warehouse where the alien ship landed, and finds the area now covered in a slime-like substance, and there are large eggs littering the floor. Garfield has a small fantasy about plus-sized omelettes, but quickly snaps back to reality when he sees a gigantic egg sac, then looks closes to what it's attached to, a larger version of the long-headed creatures, with a drastically different looking headpiece.
The creature spots Garfield and the girls and hisses at them. Just then, the masked figure from before comes in through the roof and roars at the larger creature. Just then, five of the eggs open, with more of the scorpion-like creatures emerging from them. The Powerpuff Girls destroy the creatures that come after them, but the ones that go after Garfield and the masked figure latch onto their respective faces, but they easily rip them off, with the masked figure running at the large creature, with smaller ones running at the masked figure. The masked figure rips off it's mask, revealing a grotesque face. It then proceeds to battle the creatures, with the scorpion-like creature that went after latching back onto it's face, only to be yanked away once again.
The dreadlocked creature then proceeds to throw sharp discs at the eggs, causing the large creature to roar out in fury. Garfield, the dreadlocked creature, and the Powerpuff Girls then run out of the warehouse as the large creature tears away from it's egg sac and chases after them. The group makes it out of the warehouse as the large creature breaks out and attacks the group. A small mouth emits from the creature's main mouth, snapping at the dreadlocked creature , who stabs it with it's wrist blades and tears it out with ease. The large creature then impales the dreadlocked creature with it's tail, only to be blasted by a beam from an alien ship, destroying it and sending the dreadlocked creature falling.
The ship lands, and more of the dreadlocked creatures come out and collect the body of their comrade, and the leader pulls out a Viking sword and tosses it toward Garfield before heading back onto the ship as it takes flight. Garfield and the girls then go their separate ways.
Meanwhile, on the ship, a serpent-like creature with the mandibles of the dreadlocked creatures emerges from the creature's chest. On Earth, Garfield sits in his chair, but is surprised when a serpent-like creature with cat-like ears emerges from his chest.