Error Regarding Martin's Age
Hope I don't get jumped on too hard for this but I think there is an error in Season 9. In Season 2, Martin's mother says she's been married for forty years, and Martin ruined things by being born. This would make Martin no older than 39. Only seven years (or less) were meant to have passed between Season 2 and Season 9. Although they only filmed every other year, they always picked up no more than a few months after they left off, which would make him no older than 46 in Season 9, not 60 as was stated in the birthday episode.
Edited to add: the "Happy sixtieth" was a Port Wenn resident's joke, not the character's real age.