Other mistake: Right before Homer and Bart head to the concert, Homer has the high-pitched ringing in his ears while Marge is talking. Then just as Homer says, "I hear you. C'mon, boy," note Selma's and Patty's skin over their scoop necklines are not colored in properly, it's the same color as their dresses. (00:01:45)
Continuity mistake: When Homer stands outside the Bouvier house to pick up Marge, the home's front door has three diagonal windows from upper left to lower right. However, when Marge gets home later after the prom, the three windows are diagonal the opposite way from upper right to lower left. (00:16:10 - 00:21:00)
Continuity mistake: While Otto plays the guitar at 3:00 AM, the tuning keys on the guitar head are first facing down, then the guitar head flips and the tuning keys are facing up, between shots. (00:15:45)
Homer's Triple Bypass - S4-E11
Continuity mistake: When Nick gives the news about Homer's recovery, the books on the table next to Marge change between shots. (00:20:30)
Homer's Triple Bypass - S4-E11
Continuity mistake: When we see Bart pacing when Homer is having his operation, he is on the rug in the overhead shot and by the rug in the regular shot. (00:18:50)
Homer's Triple Bypass - S4-E11
Continuity mistake: When Krusty bursts into the room, the shot ends with him having his arms and legs bent. In the next shot, he's straight as a ruler. (00:15:10)
Homer's Triple Bypass - S4-E11
Continuity mistake: When we see Lisa in Sunday school, the colour chair she is sitting on changes from blue to brown as she talks about her dad being very sick. (00:14:40)
Homer's Triple Bypass - S4-E11
Continuity mistake: When Bart says about a train wreck near the start, the items on the table between his and Lisa's bowls changes between shots. (00:02:50)
Revealing mistake: Part of Homer's right arm flashes white when he asks his father for $15,000. (00:08:50)
Continuity mistake: When we see Marge leave Bart with Patty and Selma, they are stood with a gap between them. Camera changes to focus on the sisters, and they are now next to each other. (00:06:30)
Continuity mistake: When lying on the sofa at the start, Bart's raised leg switches between instant cuts. (00:02:30)
Other mistake: When Moe is running to the Simpsons' house there is a shot of him running past the moon. When running back to the bar, the same shot is used but is simply flipped. Note the house and rocks. (00:18:20)
Continuity mistake: When Moe confronts Jimbo, Jimbo has his back in a corner with just a cabinet behind him. When the shot changes he is next to the green chair. (00:19:00)
Continuity mistake: When Bart is out in the hallway being attacked by the wolf, he is missing his right shoe. When he goes into class he is missing his left shoe. (00:18:40)
Continuity mistake: When we see Krusty with a bird on his head, the claws' position on Krusty's head change. Note his left eye. (00:16:20)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.