Other mistake: At the end of the episode, the evil Shan is texting with (most likely) Moriarity. She is sitting at a desk facing a wall and yet the laser targeting ray appears directly on her forehead, which could only come through a window directly opposite her.
His Last Vow - S3-E4
Other mistake: The helicopter that takes Sherlock and Watson to Magnussen's house is the same one Mycroft arrives in later. Tail number G-VGMG.
Other mistake: Watson never orders, but somehow while in Angelo's, he has a full plate of pasta.
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.
Chosen answer: That line of dialogue has never actually been spoken in any of the Sherlock episodes, during seasons 1-4. However, that line is written in someone's fan-fiction story online, where it's said by Sherlock and directed at Anderson.
Super Grover ★