Sid's shirt is seen black when he picks up the money bag, making it look like his shirt is the same color as his jacket.
When Gerald walks away from the table Arnold is sitting at, there's a layering error, making it look as if Gerald walks behind Arnold, but in front of Arnold's chair.
At the playground, Harold's belly becomes blue for a moment.
Although the bags were paper, Sid said they were plastic.
When Sid says "I say we make him admit that he took that money!", his first two words are muted.
Brainy and Nadine disappear at multiple points while carrying Arnold to the tetherball pole.