When the show was first brought back in 2005 there was some uncertainty of how Nu-Who fit into the existing continuity. Daleks were there and there was vague talk of the Doctor's past, but it took a while for the show to all-out recognise the older version. This was obviously quite important in engaging a new audience, with the mystery of the Time War providing an ongoing plot thread. As time went by the show started to reference older episodes more and more to the point where there's more call-backs in one episode than the entirety of Star Trek Into Darkness. This season alone, among lots of other little winks, Deep Breath built on the steampunk robots from The Girl In The Fireplace and Into The Dalek heavily invoked Tom Baker's dilemma from Genesis Of The Daleks. It makes the show rather impenetrable to newcomers and even casual long-term viewers can feel a little out of their depth. As nice as the Matt Smith cameo was in the final moments of Deep Breath, it really only serves to hammer home how much the show cares about getting people thinking about how great the show has been, rather than how good it can be now.
