After the level "Enter the Cheatrix" is completed, three more levels open up at the Simpsons house backyard. These can be taken in any order but, following the story, this is the next level.
The aliens are now stealing from the Springfield Mall using their tractor beam. The only time a security guard comes in is when one of the aliens urinates in the fountain, and he is transported to a spaceship. Cletus then comes angry to tell the aliens to stop stealing the mall, since he got a lot of coupons for televisions. The aliens transport him into one of the spaceships to explore him using a probe (with one of the aliens slipping on a rubber glove to suggest a body cavity search), and Bart and Homer go to defeat the aliens.
Everything around the mall has been destroyed, including the parking lot, which has huge holes with fire at the bottom, big trucks, and the mall itself. Homer crosses one of the holes as "Heli-Homer", and then activates a pipe that drops water to the fire at the bottom of the chasm, which releases water vapor that Bart uses to get to the other side as Bartman. Homer continues crossing the chasms and defeating aliens until he gets to a roofless Kwik-E-Mart and, when Bart gets to this place, they both step on the carpets to open the doors. When he allows Bart to get to him, they both step on the entrance so the doors open. Now, they see lots of aliens in lines that attack Homer and Bart and, as they get closer, the aliens go faster.
When they defeat three waves, a tractor beam transports them to a spaceship, in which Cletus and a pig are trapped. Homer and Bart release Cletus and he decides to help them get rid of the aliens, using his rifle. The floor goes up a level, with alien portals, and thousands of aliens who come infinitely until Homer disables the portals as Homer Ball. Then, a pink console appears and, when activated, a platform raises and Sideshow Bob comes from it.
He helped the aliens with the invasion and after a Shakespeare reciting (much to Homer and Bart's confusion), he steps on a rake that hits him on the face.Kang and Kodos are watching from their spaceship, and Kang blames Kodos for leaving his rake on the floor. Kang then steps on another rake that hits him on the face, just like Bob.
Invasion of the Yokel-Snatchers characters
Homer: Homer is one of the playable characters, he can jump, kick, burp, turn into Homer Ball, Heli-Homer and Lava-Homer.
Bart: Bart is one of the playable characters, he can jump, kick, use his slingshot, open his cape to release bats and turn into Bartman to glade, grapple and climb walls and ziplines. He can also turn into Robo-Bart (only in the Xbox version).
Cletus: he is kidnapped by the aliens and transported to a spaceship to explore him with a probe. When he is freed by Homer and Bart, he helps them defeat the aliens shooting at them with his rifle.
Aliens: enemies throughout the level, who come from postlights on the street and portals in the spaceship. They can either wield boards with nails (like in "Treehouse of Horror II") or laser belts.
Sideshow Bob: An ally of the aliens who makes a cameo in the final cutscene of the level. He states a poem of his own creation to Bart and Homer, but as he tries to step forward to attack, he gets hit by a rake (which is a running gag in the show itself).