Continuity mistake: The bible that Reverend Lovejoy returns at the library is bigger in the first shot.
Continuity mistake: Right at the beginning, the first shot of Homer and Lisa shows the door open. After Homer says 'in the most wicked condition' and the shot changes the door is closed.
Continuity mistake: When Lisa is in Principal Skinner's office, there isn't a scoreboard control panel on the desk, yet when there is an overhead shot of his desk, one suddenly appears.
The Old Man and the C Student - S10-E20
Continuity mistake: Springy the Olympic spring that Homer makes has 9 coils. Then we see the large version that has many coils, at the Olympics meeting. Homer's original spring is in his hand and now it has many coils also. When it cuts back to the stage, the large spring has few coils, like the very first time we saw Springy.
Thirty Minutes Over Tokyo - S10-E23
Continuity mistake: Marge loses one of her shoes in the "lava" , but when they fall down, Marge wears two shoes again.
Wild Barts Can't Be Broken - S10-E11
Continuity mistake: The Springfield Isotopes win the championship at Springfield Stadium and it's daytime. But Homer and the guys watch the game live on TV at Moe's Tavern, and it is nighttime.
Sunday, Cruddy Sunday - S10-E12
Continuity mistake: When Homer tells Lisa who is going with him to the Super Bowl, he says Comic Book Guy is going. In the shot showing the people lining up, Comic Book Guy is not there. He then appears on the bus later on.
Continuity mistake: When Bart says "Everybody, come quick!", the fridge door goes from open to closed.
Thirty Minutes Over Tokyo - S10-E23
Continuity mistake: When Homer breaks into Flanders's house there's a shot of the refrigerator and nothing is on it. In a closer shot, there are tickets being held up by a magnet.
The Old Man and the C Student - S10-E20
Continuity mistake: The springs on Homer's hat change size when Agnes answers the door to him.
The Old Man and the C Student - S10-E20
Continuity mistake: When Homer offers Lenny some nuts a spring pops out and gets Lenny in the left eye, but the next time we see Lenny it is in his right eye.
Continuity mistake: After Homer falls asleep at the wheel the truck starts to turn the corner. As its going around the bend you can see a white line on the road. The following shot the line has disappeared.
Continuity mistake: In this episode and maybe in other one, the door to the basement is at the entrance of the house, but that's a closet in other episode.
Tree House of Horror IX - S10-E4
Continuity mistake: In "Starship Poopers," Kang always wears a glass thing on his head, but whenever Homer beats him up, it's gone.
Continuity mistake: When Homer is talking to the makers of Police Cops, the person on the far left's hair changes from brown to grey instantly between shots.
When You Dish Upon a Star - S10-E5
Continuity mistake: In the shot just before Alec gets hit by a tree branch, his watch is missing but in the next shot, his watch gets snagged on something.
The Wizard of Evergreen Terrace - S10-E2
Continuity mistake: When Lenny is telling his story, his 5 o'clock moustache keeps changing from brown to grey.
Marge Simpson in 'Screaming Yellow Honkers' - S10-E15
Continuity mistake: After Marge pulls out of the Store, she gets stuck at a traffic jam. But when she does pull up, all of the groceries in the back have disappeared.
Continuity mistake: When Lisa finds the doorbell Marge wanted and she plays it, it is gold, but when Marge picks it up it is grey-ish.
Simpsons Bible Stories - S10-E18
Continuity mistake: Homer as Solomon cuts the pie into a roughly 1/3 and a 2/3 piece, but when he picks the pieces up, it's more or less halved.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.