Continuity mistake: Level 12 "Grand Theft Scratchy" cutscene: When Marge tells Poochie that even he isn't "extreme enough to resist the power of a stay-at-home mom, with too much time on her hands, " Poochie is wearing two bracelets, but next shot both bracelets have vanished, then continues to reappear (even within the same shot) and disappear again.
Continuity mistake: Mob Rules: When Martin runs into the road and tells Ned to stop his car, there are two white lines across the road in front of the car. After Martin drives off, the two white lines across the road have suddenly vanished.
Continuity mistake: Enter the Cheatrix: When Bart and Lisa are first in the Game Engine, they are standing side by side on two different sections of the floor. From a reverse angle, they are suddenly standing on the exact same section of the floor.
Continuity mistake: Bartman Begins: When Bart first discovers The Simpsons Game manual, the manual lands in a 12 o'clock direction in front of Bart. Next shot, the manual has shifted to a 9 o'clock direction, then to an 11 o'clock direction.
Other mistake: Big Super Happy Fun Fun Game: When Homer is crossing the bridge in the lava part of the level, as he reaches the second half of one of the logs, he begins to weigh down the log. If you switch to Homer Ball, he logs becomes less weighed down than when he was regular Homer, despite the fact that Homer Ball is basically an obese and more overweight Homer.
Continuity mistake: Big Super Happy Fun Fun Game: The first part of the level consists of Homer and Lisa defeating the Dirt Sumos. But as soon as the cut scene starts, all of the sumos have vanished. Even the ones that weren't defeated.
Other mistake: Grand Theft Scratchy: Two shots after Marge says "I just don't understand why Bart would want to play this game" shows three cats in a car pulling up to shoot three mice walking on the street. The cats take out their guns, aim straight at the mice and start shooting at them. The shot then cuts to the mice, completely unharmed and start shooting the cats. Before the shot cut to the mice, the cats were shooting their guns for a full 1-2 seconds. If the cats had their guns aimed directly at the cats and started shooting, even for this short amount of time, the mice would already be dead even before they could take their guns out.
Other mistake: Level 5 "Mob Rules" cutscene: After Lisa gives Marge the manual and explains Marge's superpower to her, when Marge shouts, "Okay, let's stop that video game," Lisa's moving head was not properly edited by the layout artists, note that Lisa's head and neck are disconnected from her body, which is a bit creepy looking as she moves her head.
Other mistake: Level 10 "Bargain Bin" cutscene: When the spaceship flies over the house all the Simpsons walk out the front door, and in this overhead shot part of the house is missing, note the animation is incomplete behind the roof of the garage.
Continuity mistake: Level 10 "Bargain Bin" cutscene: When the alien mothership hovers over the Simpson house, the green door mat is on the step in front of the door, but when Homer freaks out the green mat has vanished, though it reappears when they start running.
Continuity mistake: Level 13 "Medal of Homer" cutscene: Right before Homer receives the keycard, when the military truck drives into the village, in this shot the "Hellfish" illustration on the door is reversed and "Hellfish" is written backwards, then it's fine in the following shots.
Continuity mistake: Level 14 "Big Super Happy Fun Fun Game" cutscene: When Milhouse hands over the keycard to Homer, he's holding it out upside-down, but in the next shot the keycard is rightside-up while he's still holding it out to Homer, but it's upside-down again when Homer takes it.
Continuity mistake: Level 15 "Five Characters in Search of an Author" cutscene: When Marge and her family walk over to Matt Groening, who's lying on the floor, we see that Marge has nothing on her back, but when Matt thanks Marge for saving him the empty baby carrier is now on Marge's back, though it vanishes again when Matt kneels in front of Lisa. As an aside, the baby carrier has two shoulder straps and a waist strap, but after Matt's escape when the carrier reappears on Marge the shoulder straps are gone, so it's pretty bizarre that Maggie could stay put in it.
Continuity mistake: Bargain Bin: When the mothership starts firing at the Simpsons, Homer drops the clipboard and pencil he was holding and it lands on the ground. Two shots after, the clipboard and pencil have disappeared. It couldn't have been out-of-frame because when it lands on the ground, it is in line with the path leading to the house, and the area surrounding the path is shown two shots after.
Continuity mistake: Enter the Cheatrix: When Bart and Lisa walk up to the Rift Portal after saving Frink, the device attached to the side of it changes design between shots.
Continuity mistake: Enter the Cheatrix: There is a machine next to Bart, Lisa and Frink when they reunite in the end cutscene. This machine has three sections to it. When the shot cuts to Bart and Lisa, all three sections of the machine are visible in the shot, but Frink cannot be seen in the shot. Then the shot cuts to Frink (with all three sections of the machine being visible in the shot), and Bart and Lisa cannot be seen even though they should be right next to it.
Continuity mistake: Enter the Cheatrix: When Bart and Lisa walk up to Professor Frink whilst he is climbing down the ladder, the machine next to them has a couple of dials on them. Around these dials are a series of small lines (presumably a way of measuring different gauges). When the shot cuts to focus on Bart and Lisa, these lines around the dials have disappeared. A small arrow attached to the dials also disappears.
Continuity mistake: Game Over: Whilst God is explaining the Planet Earth game to the Simpsons, Maggie's face has light cast on it. But later in the cutscene, after the flashback of God losing the manual, Maggie's face is suddenly shadowed.
Continuity mistake: Game Over: When Homer tells God "It's time for some answers", his hands are raised and placed against each other. When the shot cuts, his hands are at his side.
Continuity mistake: Game Over: When Benjamin Franklin is telling Lisa she's a bigger butt-kisser than Thomas Jefferson, he is holding a coffee cup with his hand at the bottom of the cup. Two shots later, his hand is suddenly further up the cup.