This slipup is actually evident in two episodes; one somewhere in the middle of the series' run life (Don't remember when), and again during the two-part flashback episode just before the series finale.

Tim is talking with Randy in his bedroom while Randy works on his laptop computer. After they finish talking, Randy asks Tim if he wants to play a game on the computer, and he agrees. He then proceeds to open the game, but mentions "It will take a while to load, this thing still has a 286 chip on it and isn't very powerful."

The problem: The style of Randy's laptop computer is that of an older Apple Powerbook. Other than one rare Mac/DOS hybrid desktop system that Apple made in 1994-1995, no Macintosh or Powerbook has ever used Intel or Intel-compatible processors in their systems, which is what a 286 processor ("chip") is.