Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Harold the Butcher: When Mr. Green tells Harold his week is up and that Harold is done paying him back, both of their aprons have a white oval patch with "Green Meats" printed on it. As the scene continues, the white oval patch vanishes from Harold's apron entirely, and Mr. Green's apron patch loses its white background. (00:18:40)
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Harold the Butcher: At Mr. Green's meat store, there are at least two instances that the word "MEATS" is misspelled as "MAETS" on the store's aprons. When Mr. Green gives Arnold the package for Grandma, Green's apron changes to the misspelling. Then, when Harold returns to help Green with the crowd of customers, Harold's apron has the misspelling.
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Helga Blabs It All: While Helga is in the ventilation shaft, when she calls Phoebe for help, the rope is tied around Helga's waist with a knot at the front, but it cuts to a closer shot and the knot vanishes.
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Helga Blabs It All: After Helga successfully snatches the message tape, when she rushes out of Sunset Arms the front door is missing its handles, but one handle reappears when Campfire Lass and other girls chase after Helga.
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Helga Blabs It All: Phoebe stops the Jolly Olly ice cream truck and gets inside. As they head toward Arnold's house, in the interior shot a rearview mirror appears on the windshield where there wasn't one. Then, when the ice cream truck is parked in front of Sunset Arms, there are some changes to its appearance.
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Helga Blabs It All: When Helga falls from the vent opening, she knocks the telephone and answering machine onto the floor. Just as Helga notices the tape in the answering machine, the push button telephone has changed to a phone with a rotary dial. It then changes back to push button. (00:10:05)
Helga Blabs It All / Harold the Butcher - S3-E1
Continuity mistake: Helga Blabs It All: While Helga goes after the tape at Sunset Arms, room numbers repeatedly change/vanish, or doors disappear and reappear. Some examples: Door 3 vanishes when Helga lowers herself via rope the first time. When Arnold unfolds the attic stairway, the closest doors are 7 and 8, but when Arnold and Gerald run down those stairs, door 8 changes to door 1. When Grandpa talks to Mr. Hyunh, door 1 is now door 3. When Grandpa and Ernie enter Hyunh's room, door 7 becomes door 5. When Grandma exits door 4, it then changes to door 2.
Timberly Loves Arnold / Eugene, Eugene! - S5-E22
Revealing mistake: Timberly Loves Arnold: When Lila says, "That is, if Arnold doesn't mind making it a threesome," her left eyelashes disappear for one frame. (00:05:50)
Grandpa's Packard / Phoebe's Little Problem - S5-E19
Audio problem: Phoebe's Little Problem: When Harold wets his pants at the end, Stinky can be heard saying, "Harold wet his pants," but in the shot, he is actually laughing. (00:11:39)
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)
Helga's Masquerade / Mr. Green Runs - S5-E2
Other mistake: Mr. Green Runs: When Green tells Arnold he can't be himself and needs to come up with some fancy words, Arnold is wearing a "Vote Green" button. Then, just as Green says, "I gotta get outta here," Arnold's button now reads "Voet Green" with Vote misspelled.
Part-Time Friends / Bio Square - S2-E19
Other mistake: Bio Square: While Phoebe and Stinky are telling the class about their science fair experiment, just as Phoebe shares that it was in honor of her hero, "I.P. Pavlov," watch as Stinky's eyes move off to the side of his head, then the animation layer of his eyes return to normal.
Weird Cousin / Baby Oskar - S4-E11
Continuity mistake: In "Baby Oskar" when Suzie answers the phone there are 12 buttons on the phone, but when she is sitting on the bed there are 9 buttons.
Character mistake: The first time Arnold tries Rhonda's marriage predictor test, he says his favorite number is five, but Rhonda actually makes six moves. The second time, Arnold says it's three, but Rhonda counts off four.
The Aptitude Test / Oskar Gets a Job - S3-E9
Plot hole: Mr. Simmons asked that each student put their name on the test folders, but the folders already had names on them when he handed them out.
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.
Arnold Saves Sid / Hookey - S2-E7
Other mistake: The clock in the police station looks like it says it's after 5:00, but school is in session.
Monkeyman! / Buses, Bikes and Subways - S5-E1
Continuity mistake: Mr. Simmons counts 30 students in the bus, but nowhere near that many got off (nor have nearly that many fourth graders ever been shown).
Steely Phil / Quantity Time - S2-E12
Continuity mistake: The digits on Arnold's clock get bigger and change shape while he's talking to Grandpa.
Casa Paradiso / Gerald's Tonsils - S3-E3
Other mistake: Gerald's doctor's name is spelled "Murray Stieglitz" on the sign, but "Steiglitz" in the credits.
