Continuity mistake: When Principal Skinner is speaking to Marge and Homer, Homer is lying on the settee and you can see there is nothing beside it, but in the next shot his beer can appears from nowhere.
Continuity mistake: When Principal Skinner rings the doorbell of the Simpsons' house, the handle on the door is pink. But when Marge is at the door, the handle is now light blue.
Continuity mistake: When Principal Skinner and his mother are with Bart and his friends after the toilet prank, you can see Bart has Milhouse, Richard and Lewis are beside him. In one shot, Bart is on his own and the other three boys have gone, and in the next shot, they are back again.
Continuity mistake: Bart throws in a microscope in the cupboard of his bedroom when his mother leaves, but in the next shot the microscope is nowhere to be seen.
Continuity mistake: When Marge leaves Bart's room, you can see there is a cap on the mirror on the drawers, but when we see a full view of the room a couple of shots later, the cap has gone.
Continuity mistake: When Bart discovers a pink box by his bed, you can see there is nothing hanging out from the drawer behind him, but in a close-up of Bart in the next shot, a sock suddenly appears.
Continuity mistake: When Homer falls down the stairs, the toy clown lands behind him and a close-up of Homer shows an orange plant pot by the stairs. But when we see a overhead view of Homer lying down, the plant pot is nowhere to be seen.
Continuity mistake: When Marge enters Bart's bedroom, on the wall you can see a picture of a space rocket and on it there is a red cloth. But when we see a close-up of Marge in the next shot, the cloth has gone.
Continuity mistake: When Agnes meets Bart and his friend, it cuts to Skinner, then to Bart's group and quickly back to Skinner. When it goes to Bart's group (before Skinner) Lewis is yellow like the rest, in all other scenes he is black.
Revealing mistake: When Homer enters the Kwik-E-Mart, the automatic door doesn't fully open, and Homer's left arm goes right through it. (00:03:40)
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)
Character mistake: In the scene where the imposter Krusty is robbing the Kwik-e-mart, Krusty's hair is blueish green just like the real Krusty, but when Homer is describing the robber he says the the crook has red hair. This is so you have more clues on who the real impostor is. The imposter Krusty is really Sideshow-Bob who has red hair. (00:04:20 - 00:05:05)
Continuity mistake: Before Krusty is arrested, he grabs a drink and there is no olive in it. When he sits down, an olive has appeared in the drink. (00:05:35)
Continuity mistake: When the cops pin Krusty to the carpet, he moves further away from the yellow stripes between shots.
Continuity mistake: When Sideshow Bob is shouting and screaming just before he is taken away in a police van, Lisa and Bart swap places right before Bart says "Take him away, boys."
Continuity mistake: In the initial robbery at the Kwik-E-Mart, Apu doesn't realise what's going on until the fake Krusty demands the money from him. Yet in the video shown in court, he turns to face the fake Krusty right as Homer screams.
Other mistake: Apu already knew Homer because in the flashback episode, Homer's Barbershop Quartet, they were in a band. However, in the scene where Homer enters the Quick-E-Mart, Apu refers to Homer as steady customer as if he didn't know him.
Continuity mistake: When we see the wide shot of Sideshow Bob being handcuffed, the reporter standing behind Bart and Lisa is wearing a purple jumper. But in the shot of Bart saying 'Take him away boys', the reporter is wearing a green jumper.
Continuity mistake: When Marge is throwing all the Krusty merchandise into a bag, the bag changes from grey to brown between shots.
Continuity mistake: In "Krusty Gets Busted", Krusty's natural skin colour is established as yellow. In "Brush With Greatness" we see him wiping off the clown makeup to reveal that he has yellow skin. But in "Homer's Triple Bypass", he comes to visit Homer, with his white clown face, and tells him that "this isn't make-up". Other episodes after that also show that his skin is white.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.