We have no idea how this piece of magic was made, but with a little CGI foolery and some expert layering, Sherlock and the Doctor are finally capable of meeting. And with an extra-important Christmas special coming up for Who, and Sherlock back in the New Year, it’s exactly the sort of present we never knew we wanted until now.
But he can’t really leave John behind, can he? He already did it for two years, he can’t do it again!