Parents Day - S5-E6
Continuity mistake: In the scene where Arnold's parents leave for the last time, Grandma's hair is dark at first, then it becomes purplish-gray.
Parents Day - S5-E6
Continuity mistake: In the tricycle section of the last event, the chinpiece of Helga's helmet keeps switching colors.
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.