Factual error: Although cars are seen driving on the right-hand side of the road for most of the film, one overhead shot shows UK-style "give way" lines across the left-hand side of the road.
Audio problem: When Spiller throws the rope in the milk bottle trying to pull Peagreen out, you can hear him straining and grunting to keep a hold of it but his face and mouth are both relaxed.
Factual error: When Arriety and Spiller are rescuing Peagreen from the bottle, Arriety introduces Peagreen to Spiller. But later on when her parents show up and she introduces Spiller to them, she also introduces Peagreen to Spiller again.
Suggested correction: She forgot that she had introduced him already. People forget things all the time.
Continuity mistake: When Mr Potter removes the stuff that the exterminator accidentally sprayed on his face, it's thicker than in the previous shot.
Other mistake: At the beginning, when Pod is climbing up the table, he does it in seconds. There's no way he could have gotten up that fast.
Plot hole: How could Pod have been sure that Pete would have all the things he needed, when he is preparing to rescue Peagreen from the milk bottle?
Other mistake: When Arrietty and Pea-Green slide along the power line, they go pretty far. They would have hit a post and gotten electrocuted.
Continuity mistake: I don't know the breed of the exterminator's dog, but she's of a different one during one shot, when he finds her after she ate milk products in the factory.
Revealing mistake: Whenever there is a bird's eye view of the town, you can see that the far backgrounds are paintings.
Continuity mistake: Right after the vacuum incident, Homily Clock goes to give Arrietty a raisin and Cheerios. She walks up the stairs holding only that, yet when she reaches the top and enters her room, a cup of milk magically appears on the plate.
Other mistake: When exterminator Jeff pulls off the foam from Potter's face, it removes his mustache from his face. In reality, it should've removed both his mustache and eyebrows, which remain on his face after he is burned by the foam.
