Continuity mistake: At the start, Lila is sitting on a bench near the school wall. However, in the shot where Sheena says, "Oh, that's wonderful," Lila and the bench are missing; then they reappear a moment later. (00:01:13)
Continuity mistake: When Pea Pod Kid is taking Rhonda's marriage predictor test, Sid is walking down the stairs behind them. In the next shot, he disappears. (00:03:44)
Continuity mistake: Phoebe is going into the school in one scene, but as the camera moves she vanishes while on screen.
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.