Just recently watched the season two finale and season three premiere of The Wonder Years, and noticed a continuity error between the two episodes (of course, I think this is the first time I saw the whole season two finale, as opposed to bits and pieces).
In the season two finale, Paul announces that his family is spending the whole summer (okay, the first day of no school until Labor Day) away, and at another point it's said that the family can't go on vacation this summer. But then in the next episode, Paul travels with the family on vacation.
The Wonder Years isn't a show with negative continuity. The episodes aired back-to-back, both in the same summer. The season three finale mentions that Winnie's parents had just gotten divorced/separated which was announced in the previous episode. The fact that the family wasn't going on a summer vacation didn't need to be brought up in the season two finale (unless it was to emphasize Kevin having a bad summer) as it wasn't a major plot point. They never show Paul's family canceling their trip or just leaving Paul home for the summer. The season three premiere doesn't mention anything about how Paul was going to spend the summer away (or that they weren't going to go on vacation but then did).