The Aptitude Test / Oskar Gets a Job - S3-E9
Continuity mistake: Oskar Gets a Job: When Arnold and Suzie are doing laundry together, as Arnold talks about how Oskar was just fooling them all, he starts walking away from the dryer. In the next shot, he is walking away from the dryer again. (00:21:16)
Arnold & Lila / Grand Prix - S3-E13
Other mistake: Arnold and Lila: When Arnold tells Lila that the writing on the wall wasn't him, as Lila says, "That's OK, Arnold," she blinks, and her left eyelid is not colored in. (00:07:16)
Arnold & Lila / Grand Prix - S3-E13
Other mistake: Arnold and Lila: When Rhonda, Lila and Nadine are talking about what Helga wrote on the wall, as Lila says, "It couldn't possibly be true, could it?", she blinks, and her right eyelid is not coloured in. (00:03:12)
The Aptitude Test / Oskar Gets a Job - S3-E9
Continuity mistake: Oskar Gets a Job: After Arnold comes home after delivering the newspapers for the second time, he runs up to the door, but in the next shot, he somehow ends up at the window. His helmet also disappears between shots. (00:19:37)
The Aptitude Test / Oskar Gets a Job - S3-E9
Other mistake: Oskar Gets a Job: On the second day that Oskar forgets to do his job, Arnold reminds him that he has newspapers to deliver. After Oskar says, "You won't believe what happened," Arnold blinks, and his right eyelid is not colored in. (00:18:56)
The Aptitude Test / Oskar Gets a Job - S3-E9
Other mistake: Oskar Gets a Job: In the beginning of the episode, Arnold and Gerald overhear Oskar arguing with a man in his room. In the close-up of Arnold and Gerald as Oskar says, "You're a big man, aren't you?", Arnold's right eyelid is not colored in. (00:12:17)
Arnold's Room / Helga vs. Big Patty - S3-E4
Other mistake: Helga vs. Big Patty: When Helga dreams about boxing Patty, as she steps back from her, she is standing in mid-air for about a second. (00:17:00)
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)
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 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)
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)
Career Day / Hey Harold! - S3-E11
Continuity mistake: There are more than 16 slips in the hat, but only 16 students in class, and only 12 hands went in to pull out slips.
Grandpa's Birthday / Road Trip - S3-E7
Factual error: Road Trip: Whenever Miriam and Helga's car is on a broken white line road, the two lanes are moving in opposite directions; lanes on broken white line roads are supposed to move in the same direction. (00:17:15)
The Aptitude Test / Oskar Gets a Job - S3-E9
Continuity mistake: Oskar Gets a Job: When Arnold and Suzie are first shown in the laundry room, the latch on the washing machine door is missing. In the next shot, the washing machine and the dryer switch places, and in the shot after that, the latch is back on the washing machine door. (00:21:10)
School Play - S3-E19
Other mistake: After Helga gets mad at Arnold in the beginning, as Helga says, "What an annoying little smarty pants know-it-all," the lunch lady's body is invisible through the glass on the counter, leaving only her upper half visible. (00:01:12)
Phoebe Takes the Fall / The Pig War - S3-E16
Revealing mistake: Phoebe Takes the Fall: When Phoebe is in Helga's room helping her study for the tournament, as Helga says, "Well, let's call it a night," her left side hair is missing, then it appears mid-shot. (00:06:54)
Career Day / Hey Harold! - S3-E11
Other mistake: Hey Harold!: When Harold's family is talking about Patty during dinner, as Harold's mother says, "We can show her those adorable baby pictures of you," her left eyelid is not colored in. (00:20:39)
Career Day / Hey Harold! - S3-E11
Other mistake: Hey Harold!: When Harold and Patty are dancing together, as Harold says, "They said I didn't apply myself," Patty blinks twice, and her right eyelid is not colored in. (00:17:00)
Arnold & Lila / Grand Prix - S3-E13
Continuity mistake: Arnold and Lila: On the bus, when Arnold tells Lila that he doesn't like her like her, Lila is smiling at him. In the next shot, she is suddenly frowning. (00:07:01)
Arnold Betrays Iggy / Helga and the Nanny - S3-E10
Revealing mistake: Helga and the Nanny: When Helga tells the other kids that her nanny was fired, as she says, "Yeah, well my dad found his lucky belt under her bed this morning," her left-side hair disappears for one frame. (00:20:06)
Answer: The show is based in present day times. Plus most cars aren't old fashtioned, I recall seeing a limo and not to mention a cherry picker, etc.