Character mistake: Higgins boasts about playing chemin de fer with Ferdinand II at the resort, but there has not been any sovereign by that name in the 20th century. (00:20:40)
Character mistake: Carlton's favourite gun is a Colt "Bisley Model", rare and produced starting 1894. When he introduced it to Magnum in the cabinet he called it a "Colt 45, vintage 1860" (or sixty-something, as Magnum started his line when he might have not finished). (00:16:50)
Character mistake: The Grim Reaper is at the party to grab the paper copy of the will - however, after Magnum is incapacitated turtle-style, the guy never bothers to actually retrieve it from the mantle he put it on, nor Magnum checks out what the piece of paper is. (00:35:05)
The Arrow That Is Not Aimed - S3-E13
Character mistake: At the end of the episode, Magnum says "You know what they say about samurai swords - you unsheathe 'em, you gotta draw blood!", but throughout the episode, Tozan drew his sword on Magnum and the villain and no blood has been drawn - in case of Magnum, there was no intention of it either.
Character mistake: Bickering with his pretend wife after risking his neck with the falling crates, Magnums says "we can stop playing house, I can go back to being a private detective, which is exactly what I should have been in the first place." Magnum has a verbal tic during the series and he fiercely corrects everyone when they call him a private eye, or detective, as he goes only by "investigator" (the I in P.I, after all). He's using the wrong word here. (00:22:35)
Character mistake: In the opening narration, Magnum says "Take my good friend Marcus, for example. I woke up one day and realised I was 32 and I'd never had a chance to be 22." In the second part of the very pilot of the series, Magnum says to Alice "One day I woke up age 33 and realised I'd never been 23."
Character mistake: As he takes the elevator for the garage, Magnum's hat gets caught in the elevator doors before the camera cuts away. It's all fine on his head when he gets out. (00:42:15)
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: Higgins addresses constantly the Prince and Princess of Turbia as "Your Majesty." For an expert of protocol as Higgins, it's quite odd to make such a mistake; "Your Majesty" is used for royalty with a rank higher than Prince (kings, emperors). Paradoxically, Magnum gets it right, calling both "Your Highness." (00:06:30)
Character mistake: Higgins is narrating one of his stories, this time implying that he helped Hemingway write "The Old Man and The Sea." Normally Higgins' stories are somewhat plausible because of factual accuracy that leaves room to be taken at face value, but here he says that it happened in "The Florida Keys, '53 or '54, it was." while "the manuscript was only in the outline stage." The novel was published in 1952. (00:10:30)
Character mistake: Higgins at the bar orders "Glencadam on the rocks", but it's been established since the pilot episode that he loathes ice in his drink of choice. (00:23:55)
