Full Moon / Student Teacher - S4-E1
Revealing mistake: Student Teacher: When Olga says, "But, nothing, baby sister!" before giving Helga detention, Rhonda and Brainy disappear for one frame. (00:17:17)
Love and Cheese / Weighing Harold - S4-E7
Other mistake: Love and Cheese: When Arnold accidentally kisses Gerald's hand on the bus, his left foot is missing. (00:02:00)
Love and Cheese / Weighing Harold - S4-E7
Continuity mistake: Love and Cheese: When Arnold and Lila's boat starts sinking, it starts to move backwards and hits a huge rock at the edge of the waterfall. When Lila almost falls and Arnold holds her up, the rock is gone. It reappears in the following shots. (00:10:07 - 00:10:40)
Grandpa's Sister / Synchronized Swimming - S4-E12
Continuity mistake: Synchronized Swimming: In the pool scene at the beginning, we see a close-up shot of Connie and Maria. In the next shot, they are nowhere to be found. The three kids surrounding the pool in the beginning also disappear. (This happens because the opening shots are reused from the episode "Sixth Grade Girls.") (00:12:01)
The Aptitude Test / Oskar Gets a Job - S3-E9
Audio problem: Oskar Gets a Job: After Oskar comes home after delivering the newspapers, as Arnold asks him, "Did you deliver the newspapers?", his mouth says, "Did you," but it never says, "deliver the newspapers?" (00:22:08)
Runaway Float / Partners - S2-E20
Other mistake: Runaway Float: After Nick Vermicelli says that the parade float is a total mess, as Arnold says, "It's not a mess," the background is of the school hallway, not Arnold's garage. (00:05:28)
Runaway Float / Partners - S2-E20
Continuity mistake: Runaway Float: When the beeper float first starts to speed out of control, in one of the shots, Helga is wearing her regular outfit, not her beeper costume. On top of that, the kids on the float are smiling and waving, not freaking out like they were before. (00:08:39)
Arnold's Thanksgiving - S3-E14
Other mistake: When Helga tells Phoebe how much she hates Thanksgiving backstage during the play, the third time Phoebe says, "Helga," the background is of Helga's living room, not backstage. (00:03:38)
Helga's Parrot / Chocolate Turtles - S4-E6
Audio problem: Helga's Parrot: After Arnold accuses Lila of flicking his ear, as he says, "Well, somebody flicked it," his mouth only says, "Well." It never says, "somebody flicked it." (00:08:38)
Helga's Show / The Flood - S3-E15
Audio problem: The Flood: When the kids go into room 315 looking for Mr. Simmons, Arnold calls out his name, and his mouth does not move. (00:20:24)
Runaway Float / Partners - S2-E20
Continuity mistake: Runaway Float: When Arnold stands up on the bike before jumping onto the parade float, Eugene's hair disappears mid-shot. (00:10:11)
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.
False Alarm / World Records - S1-E17
Continuity mistake: In "World Records", during Arnold's inspirational speech on the stoop of the boarding house, Gerald is sitting on the railing. He changes positions from sitting facing Arnold on the steps to facing the street between shots.
The Little Pink Book/Field Trip - S1-E2
Other mistake: When Arnold is reading the diary at the school the other kids ask him to read more. He says "OK, but it is the last page." There are more pages. When he starts to read, then it is the last page.
Save The Tree / New Teacher - S2-E1
Continuity mistake: In the beginning of 'Save The Tree', the tree ladder is a distance above the ground. Later on in the episode, when Arnold and his friends go to the tree house for the last time, the ladder is practically touching the ground.
Save The Tree / New Teacher - S2-E1
Continuity mistake: When Harold eats Mr. Simmons' tomato sandwich, there is a red stain from the tomato on Harold's desk. This stain disappears in later shots.
Weird Cousin / Baby Oskar - S4-E11
Continuity mistake: In "Baby Oskar" the apartment number on the door to Oskar and Suzie's apartment appears and disappears multiple times throughout the episode.
Arnold & Lila / Grand Prix - S3-E13
Continuity mistake: When Arnold, Sid, Eugene, and Stinky are arguing about the name of the go cart the name is already painted on. (00:17:20)
Coach Wittenberg / Four-Eyed Jack - S2-E16
Factual error: When the kids are bowling for the first time, the placement of the pins is wrong, and when Arnold is bowling there are 11 pins.
