Monkeyman! / Buses, Bikes and Subways - S5-E1
Continuity mistake: Buses, Bikes, and Subways: Helga wears a watch on her right arm throughout the episode. However, when Helga approaches Sheena's uncle Earl and wakes him up, her watch is missing, then reappears when Earl's boat sinks. It disappears again when Helga comes up from the water, then reappears a moment later. (00:18:59)
Monkeyman! / Buses, Bikes and Subways - S5-E1
Revealing mistake: Monkeyman!: When Arnold tells the kids that Monkeyman saved him, as he says, "He went after the two guys who were trying to mug me," he moves his right hand, and it's layered over Helga's hair. (00:01:25)
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.