Audio problem: Right after Helga is standing behind the "ARNOLD" on the pavement, when she says "Hey Arnold", her lips move as if she's saying it slowly (this is fixed in the 4th season).
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 Aptitude Test / Oskar Gets a Job - S3-E9
Audio problem: In the comic book shop, Gerald says "Ho. Touche, sir." but his mouth doesn't move at all.
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.
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
Audio problem: In the scene during recess when Arnold and Gerald are talking about tutoring Torvald, Arnold says, "Ah c'mon, Gerald"; however, when he says, "it's not going to be so bad," his mouth doesn't move.
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)
Monkeyman! / Buses, Bikes and Subways - S5-E1
Audio problem: Buses, Bikes, and Subways: When Helga and Harold are running to catch the bus, as Helga says, "The bus is leaving, you dumb oaf," her mouth does not move. (00:14:49)
Arnold Visits Arnie / Chocolate Boy - S5-E12
Audio problem: Arnold Visits Arnie: When Arnold, Arnie, and Lulu leave Arnie's house, the shot fades to them at the swimming hole. Lulu then says, "So," but her mouth does not move. (00:04:39)
Sid the Vampire Slayer / Big Sis - S5-E3
Audio problem: Sid the Vampire Slayer: When the lunch lady asks Stinky, "Garlic bread, Stinky?" her mouth does not move. (00:03:35)
Grandpa's Birthday / Road Trip - S3-E7
Audio problem: Road Trip: When Miriam points out the Wheeler Inn and Big Guy Restaurant while driving, as Helga says, "I really don't think," her mouth does not move. (00:14:56)
Helga's Locket / Sid and Germs - S5-E7
Audio problem: Helga's Locket: When Abner takes the locket from Helga at the end, Helga screams, "Come back here, you filthy pig!" but her mouth hardly moves. (00:11:42)
Arnold & Lila / Grand Prix - S3-E13
Audio problem: Arnold and Lila: Near the start, Arnold tells Stinky, "I like Lila, but I don't like her, like her." The camera cuts to a different angle before he says the last "like her," but his mouth doesn't lip sync the words. (00:01:21)
Operation Ruthless/The Vacant Lot - S1-E7
Audio problem: Operation Ruthless: When Arnold first starts repeating "Hi Ruth," the shot cuts to Gerald as he says, "Stay cool, Arnold." Arnold can still briefly be heard saying his line, but his mouth doesn't move. (00:03:42)
Save The Tree / New Teacher - S2-E1
Audio problem: Save the Tree: At the end, when Bob says, "Yeah, I'll just build my beeper emporium in that vacant lot down on Vine Street," his mouth doesn't move until the word "build." Arnold's mouth also doesn't move when he says, "Huh?" (00:11:27)
Curly Snaps / Pre-Teen Scream - S3-E6
Audio problem: Curly Snaps: At the start, Curly talks to Arnold about how good it is to be ball monitor. When Arnold says, "Well, I never thought of it that way," his mouth stops moving after the word "it." (00:01:25)
Curly Snaps / Pre-Teen Scream - S3-E6
Audio problem: Pre-Teen Scream: When Phoebe turns on her CD player and reveals her Ronnie Matthews posters in her room, she says, "Now to compose the winning contest entry," but her mouth isn't moving at all. (00:13:00)
Audio problem: Ms. Perfect: When Lila says, "Whatever you do, don't smell that cow," the boys are heard laughing, but only Stinky is shown laughing. (00:15:14)
Helga's Masquerade / Mr. Green Runs - S5-E2
Audio problem: Helga's Masquerade: When Helga and Lila are at Slausen's Ice Cream, as Helga tells Lila, "About the way you're always going around acting so nice to people," her mouth stays closed until the word "acting." (00:03:21)
