Character mistake: The party is supposed to be "One of the premiere social events of the season", but the only people invited (Higgins knows for sure who is gonna come, so it's not like there's low attendance because of the weather) are a Prince from a fictional European state nobody knows about with his commoner wife, the editor of a poetry magazine that needs Robin's funds to survive, a sports star and Robin's accountant. 5 people in total, already all in Robin's pocket, and nobody else in attendance. While you could say that having royalty and a golden glove winner is certainly noteworthy, those people don't meet anyone else. Hardly a 'social event'. (00:04:00)
Character mistake: In the episode where Henry has overdue library books, they are overdue by 5 years and 23 days. Both Henry and Monroe say in the episode that the fine is around $1000 (based on 10 cents per day due 5 years 23 days)... But in reality, using that calculation, the total would come to only $185, not $1000.
Episode #1.1 - S1-E1
Character mistake: In the opening minutes of the first episode, as the Erasmus is struggling through a storm, Blackthorne is told that the boatswain is dead. He checks the corpse and then says, "Get the body aloft," which would entail carrying the deceased up the mast. The correct order would be "Get the body topside."