Arnold Visits Arnie / Chocolate Boy - S5-E12
Other mistake: Arnold Visits Arnie: When Arnold wakes up from his dream and he screams, his collar briefly loses its colour. (00:10:38)

Arnold Visits Arnie / Chocolate Boy - S5-E12
Other mistake: Arnold Visits Arnie: When Arnold wakes up from his dream and he screams, his collar briefly loses its colour. (00:10:38)

Arnold's Hat/Stoop Kid - S1-E3
Continuity mistake: When Grandpa is telling Arnold about how how he tried to cover his head when his hair falls out, the camera cuts back to him with his arm on Arnold's shoulder and Arnold has his hat on, even though the whole story is about him losing his hat.
Crabby Author / Rich Kid - S3-E17
Trivia: The book publisher's name is "H. MacDonald"; Hugh MacDonald is a layout designer.
Arnold's Hat/Stoop Kid - S1-E3
Question: Did Harold already know that the Stoop Kid had just left his stoop the first time? He would have known that a while ago due to a large crowd in the city or even in the newspaper.
Answer: No, he did not. He is seen getting off the bus with a suitcase, so he must have not been home for a few days so there is no way he could have known.
Bowling255 ★