Abner Come Home / The Sewer King - S1-E16
Audio problem: When Arnold is playing chess with the Sewer King, Arnold jumps across the table and knocks the King over. This sequence appears to be sped up: the toilet crashes way after it is destroyed, and the King says "Noooooooooooo," yet his mouth never moves.
Suggested correction: The Sewer King's mouth does move, but it does say the line a little too late. However, the toilet crashing sound is exactly where it should be, and the scene is definitely not sped up.
Magic Show / 24 Hours to Live - S1-E18
Audio problem: Helga rides past Arnold in a bus and yells "24 hours until you die!" or something like that. Her mouth never moves- it just stays open in an evil smile.
Suggested correction: Although it's hard to make out, her mouth is moving when she says that. Also, she says "23 hours until you die!" not 24.
Tutoring Torvald / Gerald Comes Over - S1-E13
Continuity mistake: Arnold switches from his left hand to his right hand when taking the test.
Suggested correction: I don't believe it is ever established whether Arnold is left or right-handed in the series. Without confirmation; he may very well be part of the ambidextrous population that uses both. I used to write with both hands myself in school.
I do believe he is ambidextrous. In "The longest Monday" he is using chop sticks with his right hand. Many other episodes he uses his left hand to write.
Except the mistake is saying he switches hands in between shots during the test. Not that one episode he's left handed and the next he's right handed. Yes, the teacher was shown for about 1-2 seconds before the switch happened. But these mistakes should be considered valid as an actual mistake in animation rather than to suggest to the audience that for no reason whatsoever, Arnold switches hands to finish the test, and only does so when not seen.
I'm ambidextrous myself, and I often switched hands when taking tests. It was very useful for preventing hand cramps. It only takes a couple of seconds to switch the pencil to the other hand, so I don't see why Arnold can't do it within that span of time too.
Crabby Author / Rich Kid - S3-E17
Continuity mistake: In "Rich Kid" Lorenzo is introduced as a new student, but he was in a previous episode titled "Arnold's Room."
Suggested correction: Other than the few episodes where a specific time of year is taking place; these episodes are not meant to be taken to be shown in chronological order. Just roughly in the same 4th grade school year.
Tour de Pond / Teachers Strike - S2-E18
Continuity mistake: The kids' teacher in "Teachers Strike" is Miss Slovak, who was their teacher in the first season, but in the first episode of this season they had a new teacher, Mr. Simmons.
Suggested correction: Other than the few episodes that take place during a specific time of year; these episodes are not meant to be taken in chronological order. Just roughly in the same 4th grade school year.
Arnold Saves Sid / Hookey - S2-E7
Continuity mistake: The kids' teacher in this episode is Miss Slovak, who was their teacher in the first season, but in the first episode of this season they have a new teacher, Mr. Simmons.
Suggested correction: Other than the few episodes that take place during a specific time of year; these episodes are not meant to be taken in chronological order. Just roughly in the same 4th grade school year.
Arnold's Thanksgiving - S3-E14
Continuity mistake: When Joey is shown in close-up, his missing tooth looks like it's there but it's covered with something black and his missing tooth keeps reappearing and disappearing in the last scenes.
Suggested correction: Joey never appears in this episode.
Continuity mistake: Harold's age is inconsistent throughout the series. Harold has his Bar Mitzvah in "Harold's Bar Mitzvah", establishing that he is 13 years old, and in "Hey Harold!", he tells Patty that he was held back a couple years, which is why he is still in fourth grade. However, in "Helga on the Couch", he is shown in the same preschool class as the other kids, and in "The Journal", he is shown playing in the park with the other kids, and he is a baby just like all of them.
Suggested correction: It's possible that Harold wasn't the only student held back, even though he's older than his classmates. Just a thought.
So? How does that justify him being in the same preschool class as the other kids?
He was probably held back in preschool but was not mentioned.
Fair enough, but he is also in "The Journal" which took place before the kids were in preschool. He is shown playing with the other kids as a baby, and there is no sign of an age difference, even though he is supposed to be 4 years older than them at most. All the other main kid characters are around 9 years old in the fourth grade. It's highly unlikely that Harold would be around those kids as a baby.
Coach Wittenberg / Four-Eyed Jack - S2-E16
Continuity mistake: Coach Wittenburg's anchor tattoo changes color from red to purple in between shots.
Suggested correction: No, his tattoo is always red.
The High Life / Best Friends - S2-E10
Deliberate mistake: In "The High Life", there is a scene where Stinky submerges his head in a tank of water. He delivers the line, "Gee willickers, it's still ticking", and everyone somehow understands what he is saying with his head underwater.
Suggested correction: Nobody responds to what Stinky says, so there's no reason to assume that everyone understood him.
The Aptitude Test / Oskar Gets a Job - S3-E9
Revealing mistake: The test paper Eugene put back in Harold's folder is blank.
Suggested correction: The paper is not blank. Helga used a purple pen to fill in her paper, and Eugene put it in Harold's folder. The paper is filled with purple ink.