The Bonfire Of The Manatees - S17-E1
Factual error: Alec Baldwin, as an expert on manatees, says that they are also called dugongs. Manatees are found in Atlantic coastal waters and in the Amazon and tributaries. The dugong is a distinct species found in the coastal waters of the Indian and southwest Pacific oceans.
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.
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.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.