Helga's Boyfriend / Crush on Teacher - S2-E14
Continuity mistake: Helga's Boyfriend: When Helga asks Stinky to be her boyfriend, as Stinky says, "Well, could you make it a Mr. Nutty candy bar?", the trays, fork, and Helga's hands are on the table. In the next shot, everything disappears from the table, then Helga's tray and fork reappear in the following shot. (00:02:16)
Helga's Boyfriend / Crush on Teacher - S2-E14
Other mistake: Helga's Boyfriend: When Helga asks Stinky to be her boyfriend, as Stinky says, "Well, could you make it a Mr. Nutty candy bar?", you can see another Stinky sitting at the table at the far right. (00:02:16)
Helga's Boyfriend / Crush on Teacher - S2-E14
Other mistake: Helga's Boyfriend: At the start, Helga starts to profess her love for Arnold in the movie theatre. In this shot, Arnold's hair has four spikes on the right and three spikes on the left. Arnold's hair is supposed to have five spikes on the right and four spikes on the left. Also, just as Helga says, "your every action," Arnold's left side hair changes to four spikes mid-shot. (00:01:06)
Freeze Frame / Phoebe Cheats - S2-E8
Continuity mistake: Phoebe Cheats: In Phoebe's room, there is a green mat on her desk, but it is missing in all the wide shots from behind Phoebe as she sits at her desk. (00:12:50)
Freeze Frame / Phoebe Cheats - S2-E8
Continuity mistake: Phoebe Cheats: After Phoebe reads the poem from her book, it then cuts to a wide shot from behind her; only she is not holding the book anymore; she is writing on her paper with her pencil. In the next shot, she is holding the book again. (00:14:00)
Freeze Frame / Phoebe Cheats - S2-E8
Continuity mistake: Phoebe Cheats: After Phoebe reads the poem from her book, she sets the book back against the lamp, and there is a blue book under the poem book. In the next shot, the blue book disappears. The location of the lamp and poem book also changes. (00:14:05)
Freeze Frame / Phoebe Cheats - S2-E8
Continuity mistake: Phoebe Cheats: When we first see Phoebe writing her poem in her room, the red book beside her repeatedly changes direction depending on the shot. (00:12:49)
Hall Monitor / Harold's Bar Mitzvah - S2-E15
Other mistake: Hall Monitor: After all the kids run into Phoebe, when Sid runs past her and her hat comes off, we can see that the hair above her scrunchie is yellow instead of black as it should be. (00:03:44)
Hall Monitor / Harold's Bar Mitzvah - S2-E15
Other mistake: Hall Monitor: When Helga is deciding on the new hall monitor and it shows a shot facing the crowd, many kids sitting in the back are faceless. (00:02:20)
Hall Monitor / Harold's Bar Mitzvah - S2-E15
Continuity mistake: Hall Monitor: In the cafeteria, when Gerald throws his detention slips on the floor, Phoebe gives him another slip. Phoebe is first behind the railing, but in the next shot, she is in front of the railing. In the following shot, she is behind the railing again. (00:08:26)
Hall Monitor / Harold's Bar Mitzvah - S2-E15
Other mistake: Hall Monitor: When Helga chooses Phoebe to be the new hall monitor, as Phoebe is walking to the stage, Iggy's hair is incorrectly coloured black instead of brown. (00:02:30)
Runaway Float / Partners - S2-E20
Continuity mistake: Runaway Float: The big beeper float constantly changes appearance during the parade. Some examples: The sign saying "Let's Go Downtown" on the front changes to "Let' Go Downtown" in one shot. The sign saying "Let's Go Downtown" on the back is missing in one shot. The orange base is sometimes blue. The blue city design around the base sometimes isn't there, and it even changes colour. (00:08:17)
Runaway Float / Partners - S2-E20
Other mistake: Runaway Float: When Bob asks the kids who wants to ride on the float, Arnold says to them it's great the way it is. In one shot, Iggy's hair is incorrectly coloured black instead of brown. (00:05:52)
Runaway Float / Partners - S2-E20
Continuity mistake: Runaway Float: When Arnold reaches the parade float on the bike, Iggy's shirt is incorrectly coloured green instead of purple. It's also green when the float rides past Mayor Dixie. (00:09:45)
Continuity mistake: Ms. Perfect: When Lila and her father are eating dinner, Lila's spoon is in her can of beans in one shot. When the angle changes and her father says, "You sure are quiet tonight," her spoon disappears from the can of beans, then reappears in the next shot. (00:19:05)
Other mistake: Ms. Perfect: When Mr. Simmons tells the class, "I have a note from Lila's father," his right sleeve briefly turns green. (00:19:22)
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)
Other mistake: Ms. Perfect: When the girls sabotage Lila's lunch, as Helga pours out Lila's milk from her thermos, the milk crosses an invisible line and disappears. (00:16:56)
Continuity mistake: Ms. Perfect: When Lila goes to Patty's locker, the books she is holding constantly change. First, she is holding two books, then three, then the red book is suddenly on top, then the red book disappears and the rectangle on the brown book changes to white, then it goes back to yellow and the blue book gets replaced by the red one, and finally, the blue book reappears (she is also suddenly not holding the locker handle, and the way she holds the books changes). (00:15:48)
Continuity mistake: Ms. Perfect: When Patty opens her locker and the jello falls on her, her head is raised above the floor, and there is no jello on her head. In the next shot, her head is on the floor, and there is jello on her head. (00:16:24)
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.