The alien invasion continues, but there are no more upgrades for the Simpsons powers, so Bart and Lisa head inside the house to use another way of cheating: internet. Bart founds a site for The Simpsons Game but just as he is about to say what they are supposed to do, Homer pushes him to play Solitaire. He opens the disc plate to put his beer on it, but when it closes itself, the beer drops into the keyboard, which produces a short-circuit that transports the Simpsons to a factory-looking place.
Lisa says it is the game engine. Then, Will Wright, the creator of the Sims, appears and tells them his latest release, "Sims Sandwich", drove him mad, so he spends his time in that place destroying old video games, one of which is "Escape from Krusty Island", and its characters are old, pixelated versions of the Simpsons. Homer and Bart need to rescue them before the game reaches the incinerator. They jump on several paths and platforms solving puzzles and eventually reach a lever that puts the incinerator off. Homer and Bart enter an elevator while Will Wright says some EA nerds caused this because they are jealous of him.
The elevator takes Homer, Bart, Lisa and Marge up to another section of the engine, above the previous one, but this resembles a fancy movie megaplex with a red carpet all over the floor, big stairways on each side that connect to a door with a mansion behind it, tubes transporting money to the mansion, posters of games everywhere and five portals with pictures of the Simpsons, four of which transport to some other worlds and one to Springfield.
The real Simpsons meet their pixelated counterparts, who tell them that to stop the aliens from invading Springfield, they will have to talk to the creator. He lives in the mansion and created all the worlds. To open the door, they have to find the four keycards, which are in the four worlds. The Simpsons then talk to Professor Frink to receive new powers. Homer gets the "Gumi-Homer" power: he can eat Gummi Venus de Milo to turn into a big gumi and shoot gumi-balls to far enemies; Bart gets the "wrest rocket" and the "super Bartman cape": his slingshot can shoot further and does more damage and his Bartman cape is bigger so he can glade further and more time; Lisa gets the "Buddha's lighting and freeze": she can use her hand to electrocute and freeze enemies; and Marge gets the "mega-megaphone": her mob can attack enemies from a distance throwing rocks or shooting.
Homer: Homer is one of the playable characters, he can jump, kick, turn into Homer Ball and turn into "Heli-Homer". He can't burp nor turn into "Lava-Homer" as there are not any power balls nor invincibility items.
Bart: Bart is one of the playable characters, he can jump, kick, use his slingshot and turn into Bartman to glade and grapple. He can't open his cape to release bats nor turn into "Robo-Bart" as there are not any power balls nor invincibility items.
Will Wright: he floats on a green diamond following Homer and Bart. He says angry comments when they solve a puzzle.
Pixelated Simpsons: they are the pixelated versions of the real Simpsons and are trapped in the "Escape from Krusty Island" cartridge which is about to be destroyed until real Homer and Bart put the incinerator off. Pixelated Homer likes donuts like real Homer.