Plot hole: When Arnold and Gerold first bump into Helge at the bus stop they ask her for bus money but throughout the rest of the movie they never need bus money.

Continuity: When Big Bob throws a model of Arnold's house in the trash it lying on its back but when it shows it again it is standing up straight.

Continuity: There's a scene where Arnold is talking about saving the neighbourhood, while Helga is on the roof of a building talking to herself. Arnold is in the street, and there's a man in a white tank top standing in front of him. In another shot, the man is standing behind Arnold, and Helga shoots a plunger at his head. Then in the next shot, the man is back in front of Arnold and his head doesn't have the plunger on it anymore.

Continuity: In one scene Grandpa packs up all of Arnold's stuff, but in the scene when Arnold and Gerold have a sleepover all of Arnold's stuff is back in his room.