Trivia: When Bart smashes his piggy bank for money, you can see that there are already cracks and tape on it. This is a reference to "Homer's Odyssey" where Homer smashed Bart's piggy bank when he was desperate for beer money.
Trivia: Smithers made his first appearance in this episode but he was mistakenly animated with the wrong colour. He was made into an African American with blue hair. This was corrected in the episode "There's No Disgrace Like Home", where he appeared in his normal yellow colour.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.