Other mistake: At Chez Pierre, after Helga asks Arnold how he likes his school, as Arnold says, "It's pretty good, I guess," part of his hair crosses an invisible line and disappears. (00:13:00)
Other mistake: At Chez Pierre, after Helga tells Arnold, "We have it all the time back home in France," in some of the following shots, Arnold's chair is completely missing. (00:13:46)
Other mistake: At Chez Pierre, when the waiter takes Arnold's menu, Arnold is mistakenly displayed in front of the table instead of behind it like he should be. (00:13:25)
Other mistake: At Chez Pierre, when the waiter takes Arnold's menu and says that he is finished with his order, Helga is mistakenly displayed behind her chair instead of in front of it like she should be. (00:13:26)
Other mistake: At Chez Pierre, after Helga talks about Paris, Arnold says, "But I thought you lived on a farm in the Loire Valley." In this shot, Arnold is mistakenly displayed in front of the table instead of behind it like he should be. (00:12:48)
Other mistake: When Arnold picks up Helga's shoe and asks Helga who she is, Arnold and Helga are getting cut off at the bottom of the screen. (00:21:39)
Other mistake: At the French café where Arnold is dining with Helga, there are several scenes where a dark line is at the bottom of the frame. It is only present during certain camera angles. Perhaps something like a hair got stuck to the animation cels, and they figured nobody would see it.
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Rex first approaches Arnold, Gerald, and Grandpa at the Tour de Pond race, as he says, "Are you two going to race that... put it on display?", Arnold's shoes are white instead of black, as they should be. (00:05:25)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Arnold and Rex's boats get stuck together during the first round, there are two shots of Sid and Phoebe at the stand. They are supposed to be sitting in their chairs, but they are misplaced too far to the left of them in these shots. This is shown again at the start of the final round. (00:07:13 - 00:08:45)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: After Arnold's boat starts sailing during the final round, Arnold and Gerald run past Rex and his team. In this shot, Arnold's hair has five spikes on the left and four spikes on the right. His hair is supposed to have four spikes on the left and five spikes on the right. (00:10:03)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: After Arnold's boat starts sailing during the final round, Rex is shown eating. In the next shot, Rex is suddenly staring at Arnold's boat in shock, but he is not supposed to notice that Arnold's boat is sailing until a few seconds later. (00:10:06)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When the wind starts to blow Arnold's boat during the final round, Arnold's right side hair changes from five spikes to four mid-shot. (00:09:50)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Grandpa runs out of Arnold's bedroom to get the S.S. Gibraltar, Arnold's hair is layered over the door when it should be behind it. (00:03:42)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Arnold and Rex are talking to each other at the end, when the camera zooms out, Rex's legs are briefly cut off before appearing mid-shot. (00:11:41)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Arnold and Rex's boats get stuck together during the first round, Sid says, "Yeah, plus they're stuck together." In this shot, the microphones are hanging from the banner, and the blue bell is hanging upside down on the side of the stand; one of the animation cels has been placed upside down. (00:07:18)
Tour de Pond / Teachers Strike - S2-E18
Other mistake: Tour de Pond: When Rex's grandfather walks up to Arnold's Grandpa at the end, Arnold's left side hair has five spikes instead of four like it should. (00:11:12)
Weird Cousin / Baby Oskar - S4-E11
Other mistake: Stephen Viksten is credited twice for voicing Oskar.
Best Man / Cool Party - S3-E12
Other mistake: In the scene where Arnold meets the gang in the alley way, they give ideas to crash Rhonda's party. When Curly tells his idea to go to the zoo and free all the animals and there are shots of the gang looking at him confused,in two of the scenes, you'll notice that when Stinky and someone else looks at him, the background is at the school, not the alley.
Other mistake: Ms. Perfect: When Lila and her father are eating dinner, as Lila's father says, "You sure are quiet tonight," the flap of Lila's can of beans is layered under her father's left arm. (00:19:04)
Hall Monitor / Harold's Bar Mitzvah - S2-E15
Other mistake: Hall Monitor: Helga tries to convince Phoebe that being hall monitor is the greatest job, with plenty of perks. Just as Helga says, "I couldn't let this job go to anyone; I picked you," Helga's hand is on Phoebe's shoulder, and part of Phoebe's shoulder is missing. (00:03:10)
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.