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)
Character mistake: Al is holding a picture of a 1965 Mercury Comet but says it is a 1972 model.
A Breath of French Air (2) - S1-E6
Character mistake: It is mentioned several times that the Larkins' holiday to France takes place in August. Whilst on the beach, Ma Larkin says that Mariette and Charlie's first wedding anniversary is the following week. However, it is established in the previous two part episode, 'When the Green Woods Laugh', that their wedding date is the seventh of July, the same date that Pop has to appear in court.
Character mistake: Eddie, Spudgun and Dave Hedgehog all appear worried at the fact that the devil takes "virgin's blood." However, it is apparent later in the episode that the 'devil' is in fact Dave Hedgehog's daughter, meaning he isn't a virgin.
Suggested correction: Also, Eddie previously slept with the Third Viscountess of Moldavia when Richie's back alley kidney donation backfired and he collapsed, so he wasn't a virgin either, but reacted as though he was.
Although theoretically correct, bear in mind that neither Eddie or Dave Hedgehog aren't particularly bright, and likely forgot they weren't virgins.
Hedgehog's daughter could have been adopted.
Character mistake: Mark walks into the house and is surprised to see Cody there, and remarks that he heard he was back. However, just before this, when Mark entered the house, Cody's van - which Mark had to walk by to enter the house - was visible through the open door, so that should have confirmed it for Mark before he saw Cody in person.
Character mistake: When King Koopa runs away from Kooky's machine, he says for it to let him go before he is grabbed. (00:08:13)