Helga's Locket / Sid and Germs - S5-E7
Plot hole: Helga's Locket: When Grandpa tells Arnold about his grandfather's Shiska-Bob Stick, he says that no one has ever touched it since his grandfather's last barbecue on July 16, 1926. However, in the season 3 episode "Grandpa's Birthday," Grandpa says that his grandfather died in 1921 while he looks at the photo album. (00:09:55)
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.