Corrected entry: Toward the end of the show, fuel is being pumped into the classic 1970 Buick wagon. The problem is that he's using the green pump, which would indicate diesel. GM didn't introduce diesel engines in passenger car until the early 80's.
Corrected entry: At the end of the movie when they are packing the car up the rear door of the Buick is a tailgate, but when Duncan gets out of the car from the back it is now a side opening door.
Correction: These tailgates opened both ways, up/down and to the side.
Corrected entry: When Susanna follows Duncan to the water park and subsequently spends the day with him, they are each riding their bicycles. But when they return home that evening there is only one bike between them.
Correction: This is because Duncan already put his bike away.
Correction: They stopped at a "BP" gas station. All pump handles are green at this brand gas station.