Continuity mistake: When Bart and Skinner are checking lockers, you can see in a wide shot that Bart needs to check seven lockers before he gets to Lisa's locker. However, Bart checks eight lockers and then opens Lisa's locker. (00:19:35)
Continuity mistake: If you watch carefully, the same footage of Bart and Skinner slamming locker doors is used. The easiest to spot is the shots of the camera at Bart from inside a locker, where a kid's scrapbook is on the left side. (00:19:45)
Continuity mistake: After Bart finds out that Lisa took the teacher's books, his Hall Monitor sash disappears and reappears for several shots. (00:20:05)
Continuity mistake: At the end of the episode, Bart is writing lines, and he has already written on one half of the board. On the half he has already written lines on, the lines go down the board about 3/4 of the way, yet when the shot changes, the lines now go all the way down to the bottom of the board. (00:20:35)
Continuity mistake: When Lisa decides to take Miss Hoover's Teacher's Edition, we see "Teacher's Edition" on the spine of the book. But when Lisa puts it in her bag the spine of the book is completely blank.
Continuity mistake: When Chief Wiggum says, "Give him your badge," he doesn't have anything on the right side (his right) of his shirt. After the camera flashes to Bart and back, Wiggum suddenly has a badge there.
Continuity mistake: When Bart uncovers the photo of the Simpsons behind the books in Lisa's locker, the books change between shots.
Continuity mistake: After Bart cleans his hands with a cloth after going to the private toilet, he puts it on his shoulder. A couple of shots later it has disappeared.
Continuity mistake: When Dolph and Kearney give Milhouse a "wedgie", they are both shorter than usual.
Continuity mistake: When Homer and Barney are talking about the lottery, Barney says, "130 million." Then, they set their mugs on the table but when they all run off their mugs have disappeared. (00:01:50)
Continuity mistake: The colour of the sign Moe switches on at the start changes from yellow to red. (00:01:50)
Continuity mistake: Homer asks Bart and Lisa what they will do with their money, Bart has a can of Buzz cola in his hand and when Lisa speaks the can simply vanishes from Barts hand. (00:04:20)
Continuity mistake: When Homer is covered in gold and goes into Burns' office, Burns has 2 folders on his desk. One yellow and one white. However, the white folder becomes yellow in one shot. (00:04:50)
Continuity mistake: When watching the draw, the family have their TV dinners on their lap, which seem to instantly disappear between shots. (00:05:10)
Continuity mistake: When Bart is in the car and asks when the dog is going to get his operation, his hand is not on Lisa's seat. When the shot changes, to show the whole car, it is. (00:07:50)
Continuity mistake: When Marge is listing all the cut backs, the calculator on the table keeps appearing and disappearing between shots. (00:10:30)
Continuity mistake: When Homer suggests the family becomes a group of acrobats, a clipboard suddenly appears on the table in front of Marge. (00:11:30)
Continuity mistake: When Bart is pacing waiting for Sant's Little Helper, the time on the clock changes drastically when the nurse opens the door. (00:11:40)
Continuity mistake: When Santa's Little Helper is eating from his bowl after his operation, the amount of food in his bowl increases drastically. (00:12:50)
Continuity mistake: When Homer tells Marge to go and get all her money, he is holding her shoulder next to her necklace. Camera changes and his hand is lower.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.