Continuity mistake: When Lisa opens the classroom door (opposite the teacher's desk) and is shocked to see Miss Hoover has returned, note the door opens outward (into the hallway) and the doorknob is on the right side of the door. When Lisa runs out of the classroom, that door now opens inward and the doorknob is on the left side of the door. (00:13:40)
Continuity mistake: When Mr. Bergstrom and Homer are eating together, Mr. Bergstrom's left hand is up and holding a fork, but the next shot shows his left hand resting on the table.
Continuity mistake: The long shot of Homer and Mr. Bergstrom eating lunch together at the childrarium shows Mr. Bergstrom's left hand resting on the table, but the next close-up shot of the duo shows Mr. Bergstrom's left hand up, holding a fork.
Continuity mistake: After Lisa paces around the school hallway practising how to ask Mr. Bergstrom over for dinner, when she opens the classroom door there's a backplate behind the doorknob and a lower panel under the window, but when she sees Miss Hoover and gasps, the backplate and lower panel have both disappeared. (00:13:35)
Continuity mistake: When Miss Hoover returns to class she writes "psychosomatic" on the blackboard, but when Lisa runs out of class the word has vanished from the board. (00:13:55)
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.