Downtown as Fruits / Eugene's Bike - S1-E1
Continuity mistake: In the Eugene's Bike episode, when Arnold has to tie his shoe, he sets his books down on a bike in a bike rack. This causes the bike to tip over and makes all the other bikes in the rack to fall down. Eugene's bike falls into the middle of the street and get ran over. When Eugene finds out his bike is destroyed, he looks at Arnold and yells. Right after this you get a good look at the bike rack. You'll notice there are no bikes in or around the bike rack.
Downtown as Fruits / Eugene's Bike - S1-E1
Continuity mistake: Downtown as Fruits: After Arnold and Gerald arrive at the school, it cuts to Helga crying about her play being ruined. When Phoebe taps her, her left arm is coming from the side of her cheese costume, but when the angle changes, it's coming from the front of her costume. (00:10:43)
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.