Sherlock: 20 Easter Eggs, In-Jokes And References
20. John Or James?
When John is kidnapped in The Empty Hearse, Mary receives a text containing a skip code - a clue to his whereabouts. One of the lines in the code is: 'John or James Watson?'
This is a reference to a continuity error in the Conan Doyle stories (which fans call the Canon). In short story The Man With The Twisted Lip, Mary Watson appears to get her own husbands name wrong when she calls him 'James!
Ever resourceful, fans came up with the idea that this was a nickname for John, and that his middle initial 'H' stood for 'Hamish', a Scottish form of James. This middle name is also present in Sherlock, memorably being used for comic relief when it is put on the wedding invitations in The Sign Of Three.