Continuity mistake: Bart's magazine appears in the second shot of him and Lisa talking, it's not in the first.
Revealing mistake: When Lisa wraps herself in Marge's arms right before she falls asleep, the inside of her mouth turns yellow.
The Simpsons (1989)
2 mistakes in Lisa the Tree Hugger - chronological order
Skinner's Sense of Snow - S12-E8
Nelson: Hey, look how much Skinner makes: $25,000 a year.
Bart: Let's see, he's 40 years old times 25 grand. Whoa, he's a millionaire.
Skinner: I wasn't a principal when I was one.
Nelson: Plus, in the summer, he paints houses.
Milhouse: He's a billionaire.
Skinner: If I were a billionaire, why would I be living with my mother? [All the kids laugh at him.] They're just not responding to logic anymore.
Trivia: Maggie scans as $847.63 in the supermarket at the beginning (not NRA4EVER, as Troy Maclure asserts in 3F31 "The Simpsons 138th Episode Spectacular), the price it costs to feed and care for the average American baby every month.
Who Shot Mr. Burns? (2) - S7-E1
Question: Chief Wiggum says that Space Invaders was an addictive video game, and Groundskeeper Willie says, "Video game?" I don't understand why he is so shocked. Could someone help please?
Answer: The joke is that Willie was so addicted to Space Invaders that he believed it was reality: every time he played, he was actually defending the Earth from dangerous aliens. It's a surprise to him that it was actually a game.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.