Favourite references to the original series?

[Red McFace]

Just started watching Sherlock recently but I immediately loved how well it was done with regards modernising it but only where it was necessary, ie Sherlock having mobile phones and getting into a black cab as opposed to a hansom.  

My favourite ref to the original series was the first episode when he talked about the phone Watson had, specifically the way there were scratches around where the charger would have been plugged in at night.  He deduces that the original owner had drinking problems from that.  That is the exact same as the first Sherlock Holmes story except replace phone with watch.  I thought it was perfect.

Anyone else have favourite references?

[Cat]

I can't remember exactly which story from the canon this is in, but it is once mentioned that there are seventeen steps up to 221b. There is video footage somewhere of Mark Gatiss getting all excited because there are exactly seventeen steps in the set as well. There are so many little things like that hidden throughout the series and I really adore how much detail is put into hiding them.

[Sara Turner]

"I'd be lost without my blogger" in place of "I'd be lost without my Boswell" is great.  I also couldn't stop laughing during the "Rachel" vs "Rache" debate.

[Bella Cannon]

I liked how they gave John a psychosomatic limp but the real wound was in his shoulder. This was nice little reference to how Arthur Conan Doyle kept changing the location of Watson's war wound in the original stories! 

[Niall M]

"Vatican Cameos" has to be one of the most brilliant, subtle references to canon in the entire show.