Odd Man Out - S3-E6
Factual error: Near the end of the episode when Kevin and Paul are riding their bikes toward each other before they stop for a brief hello of sorts, Kevin rides past a couple cars parked on the street that were built in the early 1980's. A red Pontiac LeMans and a black Pontiac Grand Prix-both were parked in front of the 1969 Ford Thunderbird.
Factual error: After the failure to get a new car, the family is sitting around disconsolately watching TV, when a commercial for a new Camaro comes on. However, the Camaro shown is a second generation unit, not introduced until February of 1970, and the Arnolds are still stuck in 1969.