Continuity mistake: When we see Skinner's car before the newspapers fall on him, it is a light-brownish color. When the police arrive, it is the same color as the cop cars. (00:19:10)
Tree House of Horror II: A Simpsons Halloween - S3-E7
Continuity mistake: During the 'Next week, on the Simpsons' clip, Maggie changes where she sits at the table. Lisa also changes where she sits, as you can see in the background. (00:21:45)
Continuity mistake: As Homer and Marge are singing in the car, there is one exterior shot of the car, showing it is yellow, but the rest of the scene it is green. (00:05:55)
Continuity mistake: When Homer helps Bart with his racer, the wall of the inside of the garage keeps changing from blue to red. (00:11:45)
Continuity mistake: When Skinner is calmly driving the bus on the way to school, they have obviously gone past a number of power lines (you can see that they have because you can see them in the background). However, when Skinner is trying to get onto the main road, the power lines have disappeared from the background. (00:12:45)
Continuity mistake: When Homer is sleeping on Bart's school floor, Bart puts his shoe in Homer's mouth. Later, when Homer is screaming about "Cobras," the shoe has been coloured black, rather than the usual blue.
Deliberate mistake: The mouth on the panda costume is in a constant smile and at no point does Homer change it, even when he is in pain. However, when he is being pulled back under the curtain the mouth is open and the mask has a frightened expression. I suppose this was done on purpose, but it's still a continuity error of sorts.
Radio Bart - S3-E13
Continuity mistake: At the start of the scene where Bart talks to Rod and Todd on the radio, their shirt colors switch. (00:08:50)
Continuity mistake: When Homer reaches into the fridge to take out the tub of triple chocolate ice cream, we see it in a brown and white striped tub. When he lifts it out, it's turned into a plain pink tub and has shrunk considerably. (00:03:50)
Continuity mistake: At the beginning of the show, the hospital Mr. Burns is at has a sign in front of it that reads, "Got Tumor?", but when we see the hospital again it isn't there. Additionally, the "Mayo Clinic" sign atop the building gets noticeably smaller in the second shot.
Homer Badman - S6-E9
Continuity mistake: Just after Marge's left jacket pocket bursts open at the candy convention the shot changes to a shot of Marge's face. The next shot her right pocket has suddenly burst as well and the candy in it is no where to be seen.
Homer Badman - S6-E9
Continuity mistake: When one of the pockets of Marge's coat explodes (when Homer is stealing the rare Gummi), a huge pile of candy comes pouring out. When she bends down to pick some up, there isn't nearly as much candy there as before. There are people picking up the candy with her, but they would have to pick it up extremely fast, and they aren't.
Tree House of Horror XII - S13-E1
Continuity mistake: In 'Wiz Kids,' we see Ralph tied up in Lord Montymort's lair. Between a wide shot and closeup, when he says "Dying tickles," his cloak goes from undone to done up. (00:17:05)
The Simpsons Christmas Special: Simpsons Roasting on an Open Fire - S1-E1
Continuity mistake: When Homer has been informed about the Christmas money being spent on Bart getting his tattoo surgically removed, he leaves the house. When he opens and closes the door to leave, the wreath on the door is white with a red bow. When Homer then turns to look his Christmas decorations, the wreath is now green. (00:08:50)
Itchy and Scratchy: The Movie - S4-E6
Continuity mistake: When Bart and Lisa are watching TV, Bart says something like 'I've got my ticket' and pats a ticket that is inside his shirt pocket (which there is none). But later in that same scene when they are still watching TV, both the pocket and the ticket have gone. (00:12:20 - 00:14:15)
Tree House of Horror V - S6-E6
Continuity mistake: When the Simpsons shed their skin at the end, the skin falls to the floor. In the next shot it's gone.
Tree House of Horror XII - S13-E1
Continuity mistake: In the end title sequence, the frogman thing vomits and leaves a stain on the parking lot. When Pierce Brosnan drives away in his car, there is no stain. (00:21:05)
Tree House of Horror IV: The Simpson's Halloween Special IV - S5-E5
Continuity mistake: At the end just before the Simpsons say "Happy Halloween everybody" they are about to bite Lisa (and make her a vampire). Maggie has no dummy (or in America, pacifier) in her mouth, but it suddenly appears when she closes her mouth. (00:20:50)
Tree House of Horror IV: The Simpson's Halloween Special IV - S5-E5
Continuity mistake: In "Terror at 5 1/2 Feet", when Milhouse decides that he is going to sit next to Uter, Uter all of sudden moves to the other side of the seat between shots. (00:12:20)
Radio Bart - S3-E13
Continuity mistake: When Homer, Marge and Sting are down the hole and Sting is digging, Homer is wearing a vest. But in the next shot when they find Bart and Homer moves Sting out of the way, he is wearing a shirt. (00:20:50)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.