Operation Ruthless/The Vacant Lot - S1-E7
Revealing mistake: Operation Ruthless: When Helga and Phoebe are chasing Ruth in the bumper car, when Ruth's car stops and Helga looks back at her, Helga's right lower leg is incorrectly layered over the bumper car seat, and Phoebe's legs are colored black. (00:08:11)
Operation Ruthless/The Vacant Lot - S1-E7
Continuity mistake: Operation Ruthless: When Helga and Phoebe's bumper car flies into the air and lands on the hot dog truck, as the people start to run away, watch for one person that disappears from the shot, then reappears, and his shirt changes from green to orange. (00:08:36)
Abner Come Home / The Sewer King - S1-E16
Continuity mistake: Abner Comes Home: When Abner comes back to the boarding house at the end, Arnold starts running towards him, and there is no mud puddle. In the next few shots, a mud puddle suddenly appears for both of them to fall into and roll in. Then in the next wide shot, the mud puddle disappears, and in the last two shots of the episode, it returns once again. (00:11:09 - 00:11:48)
Door #16 / Arnold as Cupid - S1-E10
Other mistake: Arnold as Cupid: When Oskar gives Arnold breakfast, besides the fact that the objects move from the left side of the tray to the right between shots, look at the glass of orange juice as Oskar lowers the tray to Arnold. Despite Oskar never rotating the tray around, the glass of orange juice glides itself over to the top left corner of the tray. Very weird. (00:14:34)
Magic Show / 24 Hours to Live - S1-E18
Audio problem: Magic Show: During Arnold's magic show, the kids start chanting, "Make Helga disappear!" When Helga says, "Alright you bunch of clods," they stop, but their voices can still briefly be heard. (00:03:28)
Door #16 / Arnold as Cupid - S1-E10
Audio problem: At the hat store, when Arnold says "Huh? What are you, nuts?", his lips don't move - but Gerald's do.
The Little Pink Book/Field Trip - S1-E2
Continuity mistake: On the "Presidents of the United States" sign behind Helga, the word "United" becomes "Nvited"
Das Subway / Wheezin' Ed - S1-E12
Factual error: There's no way Grandma could have connected two "live" wires with her bare hands without electrocuting herself, and there's certainly no way the wires could have stayed connected.
Operation Ruthless/The Vacant Lot - S1-E7
Continuity mistake: In Operation Ruthless, the pedal in Helga & Phoebe's bumper car changes color from black to gray to black between shots.
Door #16 / Arnold as Cupid - S1-E10
Factual error: Ernie removes two screws from a glass panel in the skylight, but then lifts the panel from the side that's still screwed in.
Helga's Makeover/The Old Building - S1-E4
Continuity mistake: When the classroom is first shown, the first two desks against the wall near the door are occupied by Curly and Eugene, Gerald and Arnold are sitting where Curly and Eugene were shown.
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.
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.
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.
Arnold's Hat/Stoop Kid - S1-E3
Audio problem: When Harold says, "Hey, what are you, scared?" his mouth stays open for the last word. It never closes for the "d" at the end.
Tutoring Torvald / Gerald Comes Over - S1-E13
Continuity mistake: Arnold and Gerald have to climb stairs to get to Oskar's apartment, but this would mean the building has three floors, and the outside views indicate that there are only two (plus the attic).
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.
6th Grade Girls/The Baseball - S1-E5
Continuity mistake: While walking down the stairs, Maria only has three toes on each foot; she has four at the pool.
Benchwarmer / Cool Jerk - S1-E11
Continuity mistake: The scoreboard has room for 10 names on each side when shown in close-up, but when Arnold is shooting free throws, there are only 7 spaces on each side.
Downtown as Fruits / Eugene's Bike - S1-E1
Continuity mistake: In the Eugene's Bike episode, when Arnold has to tie his shoe, he sets his books down on a bike in a bike rack. This causes the bike to tip over and makes all the other bikes in the rack to fall down. Eugene's bike falls into the middle of the street and get ran over. When Eugene finds out his bike is destroyed, he looks at Arnold and yells. Right after this you get a good look at the bike rack. You'll notice there are no bikes in or around the bike rack.
