Mark Gatiss is an Internet Troll
Mark Gatiss, the co-writer and co-creator of Sherlock (along with Steve Moffat) is very fan-savvy. One of his favorite hobbies is using his twitter feed to troll fans by offering them tantalizing bits of information about filming Sherlock that actually may mean absolutely nothing. Moffat has been known to do this as well, but to a much lesser extent. Perhaps the most interesting one, and the most overlapping with the exposition of the “fourth wall” is this image:
which refers to a well-known Sherlock fandom blogger. This is supposedly a picture of Martin Freeman, and it may very well be, but I personally suspect that it could in fact be Gatiss himself hiding behind the parka hood. It really is John Watson’s parka from the series, but the hands don’t really look like Freeman’s. Compare:
There could be a number of contributing factors, but given that we already know how much Gatiss likes to mess with people, it seems entirely believable that he would do such a thing.
He also posted this picture during the filming of series 2, knowing that fans would see “bed” and immediately jump to sexy, sexy conclusions, which he purposefully did not bother to correct:
Further Gatiss tweets to follow.