Sherlock (2010)

The Reichenbach Fall - S2-E3

Continuity mistake: When Moriarty puts the gum on the glass case around the crown jewels, the gum moves between shots.

The Hounds of Baskerville - S2-E2

Factual error: Sherlock finds a photo of Major Barrymore's father and says he's wearing the Distinguished Service Order. The ribbon is not that of the DSO.

Necrothesp

A Scandal in Belgravia - S2-E1

Continuity mistake: We see John come into the room and stand next to Mrs. Hudson and put on his coat. After a few shots Mrs. Hudson walks away with the plates and says, "Lovely tune, Sherlock..." As she's walking away we see John isn't wearing his coat, and he puts it on again. (00:50:00)

The Hounds of Baskerville - S2-E2

Deliberate mistake: The army major wears a full beard. British Army personnel may not wear beards. (The beard is a nod to the original canon character on which he's based, John Barrymore, who is described in the book multiple times as being a "black-bearded man").

Necrothesp

The Reichenbach Fall - S2-E3

Plot hole: For the supposed code that hacks into UK system, Sherlock deduces that the finger taps are counted as 1s in the binary code and the rest (while Moriarty's fingers are in the air) are taken as 0s. Sherlock can't know the rate at which the rests are counted in the binary code that he thinks Moriarty tapped out. So even if the key code was real, he wouldn't have known what it was.

A Scandal in Belgravia - S2-E1

Other mistake: While Sherlock sits reading the paper he gets a text alert from (we assume) Irene Adler, and John notes that he had heard this alert fifty seven times. At the end of the episode, when Sherlock is looking through the texts that she sent to him, there are not that many texts from Miss Adler.

The Reichenbach Fall - S2-E3

Continuity mistake: In the scene where Sherlock is on the roof of the hospital with Moriarty, when Moriarty shoots himself in the mouth, when the camera shot quickly changes from a close up and Sherlock moves back, the gun disappears from Moriarty's hand (to the right of Sherlock). In the next shot of him, it's still in his hand.

Liam D

A Scandal in Belgravia - S2-E1

Continuity mistake: At Buckingham Palace, Watson has just sat down next to Sherlock. There is a red pillow between then on the couch. It moves, sometimes sitting straight and sometimes tilted, between shots throughout the scene. (00:14:45)

ployp

A Scandal in Belgravia - S2-E1

Continuity mistake: Near the end, when Mycroft is talking to Watson, he folds his hands and places his head on them. However, in the next shot, his hands are a couple inches away from his face.