Love and Cheese / Weighing Harold - S4-E7
Trivia: In 'Weighing Harold', when Arnold is in the comics store, there are comics in the background referencing other Nickelodeon shows, "Catdog" and "Spongebob Squarepants." The former had aired almost exactly a year before this episode did ('Catdog' premiered on 4/4/1998 and this episode on 4/7/1999). The later aired about a month after this episode.
Dinner for Four / Phoebe Skips - S4-E5
Trivia: These were the last two episodes to be made with traditional cel animation, before switching to digital ink and paint.
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.