Today's Sherlock topic is favorite canon reference/joke.
Even though Sherlock is a modern adaptation, Steven Moffat & Mark Gatiss do a great job of including a lot of canon. I really love the way they sneak little details in throughout the episodes.
My favorite one is this one...
In the canon, Vatican cameos is a case mentioned in passing by Sherlock Holmes in Hound of the Baskervilles. Doyle never wrote a story about it. I love the way Moffat and Gatiss snuck it in there!