Character mistake: Jill mentions that her parents were married for 50 years, and her mother corrects her and says it was 51 years and 7 months. However, the season 6 episode Jill And Her Sisters was about the aforementioned ladies planning their parents' 50th wedding anniversary, and the penultimate episode of the season, Taps, saw Jill's father die a few months after the former episode. Since only a few months had passed, there's no way Jill's parents could have been married for 51 years and 7 months.
The Calculus Affair: Part 2 - S1-E13
Character mistake: After reaching the border, Snowy finds an umbrella and Tintin states that it is Calculus's umbrella. It isn't Calculus's umbrella - Calculus's umbrella has a brown handle, and this one has a grey handle. (00:42:25)