* AdaptationDisplacement: The TV series is much more famous than the series of novels it was originally based on. It's also markedly different from the original series of novels. In the books, Murdoch is much more of a DeadpanSnarker and is outright contemptuous of Brackenreid, and solves his cases through legwork and talking to people rather than any form of science. Inspector Brackenreid is depicted as an incompetent drunk who's also bigoted against the Catholic Murdoch. George Crabtree is described as having a large build and is a married father of five.
* CompleteMonster: [[FauxAffablyEvil James Gillies]] is Detective William Murdoch's ArchEnemy and one of the most dangerous men he's ever met. Initially coming into conflict with Murdoch after he murdered his professor as part of a way to [[ForScience test a theory of Applied Physics]], Gillies was defeated when Murdoch tricked his weak-willed partner, Robert into turning on him. After escaping the noose by bribing a dying man into taking his place, Gillies murders Robert by sawing his head off while he's still alive. He then initiates a [[CriminalMindGames twisted mind game]] with Murdoch that culminates in him [[BuriedAlive burying Julia alive]], with Murdoch only narrowly getting there in time to save her. Unfortunately, Gillies escapes and one year later [[FrameUp frames Julia]] for the murder of her husband, all as part of a plan to lure Murdoch into a SadisticChoice of either saving his own life or that of Julia. Fortunately Murdoch is able to alert his fellow officers, who arrive in time to save him before the [[DeadlyGas poisonous gas]] floods the room. Finally, he arranged for several criminals to break onto the train transporting him into prison, causing chaos which he used to try to escape, all the while taunting both Murdoch and Julia that they "owe him" for killing Julia's husband and allowing them to be together. Sadistic and defined by pettiness, James Gillies is the worst that Detective Murdoch has ever faced.
* EnsembleDarkhorse: There are many fans who are quite fond of Henry Higgins, and would very much like to see his character become part of the main cast. He and Constable Jackson have both been making more appearances since the beginning of season 8, often together with Crabtree, so it seems the writers have listened to some extent.
* FoeYay: Some fangirls began to ship Murdoch and James Gillies together after [[spoiler: the latter kisses the former on the mouth for a full three seconds in "Midnight Train to Kingston."]]
* HolyShitQuotient: Viewers all across the board were completely stunned when [[spoiler:Gillies kisses Murdoch rather passionately in "Midnight Train to Kingston"]]; ''no one'' saw that coming!
* HoYay: Between Crabtree and one-off character Nuniq, including a goodbye kiss (on the cheek).
* PoliticallyCorrectHistory: While the racial and sexual biases of the era are prominent in the background, and often inform the cases being investigated, the central characters seldom espouse them, and if so only during subplots that require introspection and are resolved by learning the corresponding 21st-century value:
** Murdoch, a Catholic, initially receives some stick from Brackenreid for being a "Papist", but this is dropped relatively early.
** Murdoch also must come to terms with Dr. Ogden's abortion, both as a moral dilemma and because she's his OneTrueLove.
** In one episode, Brackenreid worries that his son might be gay because he wants to play a female part in a play. This leads to the boy getting hurt badly in rugby trying to impress his dad. While the boy's ultimate reasoning for wanting the female role (she had more lines) is later revealed and accepted, it doesn't come before Dr. Ogden has to talk Brackenreid into accepting his son's possible sexuality. In an episode set nearly ''seventy years'' before the decriminalization of homosexuality in Canada.
** While initially not thrilled to discover that Dr. Grace is engaging in lesbianism, Brackenreid rather quickly ends up showing understanding for her.
** Justified in the cases of Dr. Ogden and Dr. Grace, as two rare female physicians and pathologists during that period. Indeed, Dr. Ogden's unabashed statements of progressive views led to marital strain during her first marriage to Dr. Garland. In later seasons, we see her start an underground women's health clinic teaching birth control (which she was briefly arrested for), and vehemently object to the MaritalRapeLicense of the period. Dr. Grace, meanwhile, [[BiTheWay engaged in a same-sex relationship]]. Both were involved in the nascent suffrage movement of the early 1900s.
** It is pretty safe to assume that Toronto did not have two female coroners around that time, and that the men of the time would not have accepted the idea of women working in a morgue nearly as well as they do throughout this series. However, there was at least one skilled female Canadian pathologist, Maude Abbott.
** In "The Big Chill", the term "Inuit" is used throughout the episode. The name "Eskimo" (which is considered obsolete and inappropriate in Canada today but is correct for the period) appears only once.
* TheWoobie: Whenever Murdoch breaks down and is NotSoStoic, especially when Julia told him about [[spoiler:her abortion and that it left her barren]] and implied that she wanted to break up their relationship.
* WhatAnIdiot: It's understandable that James Pendrick doesn't think much of Thomas Edison, given that the latter has been hounding him on suspicion that he's violating Edison's film technology patents. However, when you're an aspiring film director, it's probably not a good idea to turn down a job offer from the man who owns just about every movie screen in the United States, much less call him a "scoundrel" to his face.