Continuity mistake: When Marge discovers a letter for "Santos L. Halper", Bart has nothing in front of him on the table. In the next shot, a knife, fork, bowl and glass have appeared.
Continuity mistake: When we see Bart holding the post, he is initially holding it with one hand, but when we see a close-up of the post in the next shot, he is holding it with both hands.
Continuity mistake: When Marge finds Lisa's German verb wheel in the post during the breakfast scene at the start of the episode, you can see Lisa has nothing in front of her. In the next shot, a bowl and a glass have appeared.
The Old Man and the Lisa - S8-E21
Continuity mistake: Right at the start when Lisa says "I could still use more paper," the plastic can-rings she was holding vanish in the next shot.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Lisa tears up Mr Burns' cheque at the end of the episode, there is nothing behind her. But in the next shot, a lamp shade suddenly appears.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns tries to give Lisa a taste of Slurry at the recycling plant, he has a spoon in his right hand. But when we see Mr Burns a little later on, the spoon has gone.
The Old Man and the Lisa - S8-E21
Continuity mistake: When we see Mr Burns and Lisa during the recycling scene at the Retirement Castle, you can see behind them there are bags containing items for recycling, but in the next shot the bags have gone.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Lisa spots a fish trapped in a can holder on the beach, she takes the fish out of the holder and drops it on the ground. But when Lisa throws the fish into the sea, there is no sign of the can holder.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns enters the Simpsons' house, Mr Burns puts his hat on the floor and goes down on his knees and starts praying. But when Lisa is speaking to Mr Burns, the hat has gone.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Grampa Simpson says "That's the activity room" to Mr Burns at the Retirement Home, you can see that Mr Burns and Grampa both have glasses on their trays. In the next shot, Mr Burns' glass is on the table and Grampa's glass has moved from the left to the right.
The Old Man and the Lisa - S8-E21
Continuity mistake: When the two store assistants see Mr Burns looking at the Ketchup and Catsup bottles, the items on the shelves behind them change between shots.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns is looking at the Ketchup and Catsup bottles in the supermarket, there is nothing in front of him but in the next shot his trolley appears from nowhere.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Smithers tells Mr Burns to "maintain your dignity", you can see there is a cup, plate and spoon on the table. In the next shot, all three items have disappeared.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Lenny is sitting at Mr Burns' desk, you can see there is nothing in front of him on the table, but in the next shot a "Lenny" name card appears.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Smithers tells Mr Burns that his money has gone, you can see there is nothing on the blue pad on the table, but in the next shot two fountain pen holders have appeared.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Principal Skinner is at the Recycling Centre, you can behind him there are steel drums but in the next shot they have changed to newspapers.
The Old Man and the Lisa - S8-E21
Continuity mistake: When Mr Burns is speaking to his lawyers in his office, there is a blue pad on the table that keeps disappearing and re-appearing between shots.
The Old Man and the Lisa - S8-E21
Continuity mistake: When we see Mr Burns speaking to his lawyers, you can see there is a book stand on the table, but in the next shot it has gone.
The Old Man and the Lisa - S8-E21
Revealing mistake: At the hospital, while Lisa is explaining how much 10% of $120 million is to Homer, Dr. Hibbert's hand is yellow.
Factual error: You wouldn't hear a dial tone on one side of the phone line if the phone on the other side was cut from the receiver. You wouldn't hear anything.
Answer: Willy referred to an encounter he believed he had with actual aliens, while Wiggum thought he was referring to the arcade game.