The Last Of The Red Hat Mamas - S17-E7
Factual error: Milhouse says he speaks fluent Italian, but his Italian is full of basic grammatical errors. He says that "insegnante" means "masculine teacher" when the same word is used for a male or female teacher. There are errors in Lisa's Italian course too ("barca piccola" instead of "piccola barca"). Despite Lisa's understandable mistakes, as she is a learner, Milhouse never corrects her (there is no such word as "idioto"). Even Milhouse's grandmother, who is Italian, makes many grammatical mistakes.
Continuity mistake: When Homer says to Bob that he tells Marge everything, his hand is by his mouth, the shot cuts and it is at his side.
Homer's Paternity Coot - S17-E10
Continuity mistake: When Dr. Hibbert is about to reveal the results of the paternity test, Mason Fairbanks is wearing a blue blazer and black pants. But, when Dr. Hibbert points at him and says "This guy", he has a light blue sweater and blue pants.
The Seemingly Never-Ending Story - S17-E13
Continuity mistake: When Lisa pets the goat after it returns her necklace, her pink jacket is missing, in the next shot, she has the pink jacket on.
Factual error: Moe has a double barrelled shotgun that fires four times. A double barrelled shotgun can only fire two shells before having to reload.
Continuity mistake: When the jury is "oohing" Wallace Brady, Lenny's five o'clock shadow is missing. It reappears in the next shot.
The Mook, the Chef, the Wife, and Her Homer - S18-E1
Continuity mistake: Just as Otto is about to put in the grand funk tape you can briefly see an different tape in the recorder. Slow motion is not needed but a sharp eye is.
The Mook, the Chef, the Wife, and Her Homer - S18-E1
Continuity mistake: When Bart and Fat Tony's accomplices are going to meet Krusty, Krusty's nose can briefly be seen as white when it should be red.
The Mook, the Chef, the Wife, and Her Homer - S18-E1
Revealing mistake: When Fat Tony says "The Calabresis. My archenemies in waste management." while driving the carpool, a huge line briefly appears around his cheek and mouth.
The Mook, the Chef, the Wife, and Her Homer - S18-E1
Continuity mistake: When Lisa grabs Ottos tape recorder her necklace is orange but when she gets off the bus it is white.
Please Homer, Don't Hammer 'Em - S18-E3
Continuity mistake: It is revealed that Bart is very allergic to shrimp. However, in "The Frying Game" (where Marge and Homer get "framed" for a murder and end up on "Frame Up"), Bart says he was in the green room and that he "ate so much shrimp."
Please Homer, Don't Hammer 'Em - S18-E3
Continuity mistake: As the workmen begin to leave site after hearing that Homer is unable to pay them, a couple of tools are dropped on the ground; however, in the following shot, facing back towards the cabinet where Homer is hiding, the tools have disappeared.
Please Homer, Don't Hammer 'Em - S18-E3
Continuity mistake: In this episode Principal Skinner breaks into Bart's doctors office to find out if Bart has a 'kryptonite'. Bart discovered Skinner was allergic to peanuts. On Bart's medical history form under 'known allergies' it has shrimp ticked (they later battle with shrimp and peanut on a stick). However in a previous episode (The Heartbroke Kid, season 16 episode 17) it was discovered that he was allergic to cauliflower, so that should have been on the list as well.
Continuity mistake: When Homer is eating donuts while everyone is doing push-ups, his donut stays the same size every time he bites it.
Other mistake: When Moe is rolling his eyes after saying it was the first time he poured beer into the water supply, Herman's face is drawn incorrectly.
Other mistake: At the end when Bart and Homer are singing "twinkle twinkle little star" Bart's tongue is green.
Other mistake: When Homer is being interviewed while feeding baby Lisa, there's a picture of 8 year old Lisa in the background.
Continuity mistake: When Marge enters "Your home from space" the address is still http://www.google.com, then the shot changes to Marge outside and then shows the computer again where the address is now http://yourhomefromspace.com.
Stop Or My Dog Will Shoot - S18-E20
Continuity mistake: In the scene where the dog chases Snake into a playground, Santa's little helper starts pulling the ropes off the top of the climbing frame, in one shot the dog has two ropes left but when we see Snake the dog chews through one rope and the whole thing falls.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.