Ever since the Tenth Doctor defeated the Master, there has been rumors and theories about the next regeneration of the Master. The last time that we saw the Master, he sacrificed himself to save the Doctor. That has not stopped Doctor Who fans across the globe from coming up with theories about who is really the Master. There were theories that Rory was the Master, that River Song was the Master, and that Clara was the Master. None of these theories panned out.
New theories have emerged this season stating that Danny Pink is the Master and that is why the same actor played both Danny Pink and his grandchild Orwell Pink. The same actor was used because both Danny and Orwell are the same person. Then the little boy in the barn to whom Clara gives the soldier toy is the Master and not the Doctor. Or course, another common theory about the current season is that Missy is actually the Master and the Nethersphere is the latest effort to take down the Doctor.
But perhaps the most outlandish Master theory is that the Twelfth Doctor himself is actually the Master. That’s right, the Doctor is the Master. This theory is born from the fact that the transformation was not seen on screen as it has been previously, and the fact that the Eleventh Doctor somehow made a phone call to Clara during the regeneration. The idea is that the Master, who is acting as the Doctor, snuck into and stole the TARDIS during the regeneration and locked up the real Doctor within the TARDIS, or just left him stranded in Trenzalore.
These theories on the return of the Master have multiple holes in them, but the biggest isn’t the Doctor Who canon or continuity but the person running the show, Steven Moffat. When Moffat took over with the changing of the Doctor from David Tennant’s Tenth Doctor to Matt Smith’s Eleventh Doctor, the series was essentially rebooted. The TARDIS got an upgrade, the theme music changed, and all of the previous companions, friends, and known enemies were left behind. With a few rare exceptions it was like all the previous incarnations of the Doctor never happened.
While the basics remain the same – Doctor good, Daleks and Cybermen bad – the familiar characters were gone. We have not seen nor heard about Sarah Jane, Captain Jack, Martha Jones, or Donna Noble in years. Rose Tyler made a memorable appearance in the lead up to the end of the Matt Smith era, but was never referred to by name. Likewise, some of the greatest villains whom the Doctor had faced in the pre-Moffat years, like the Master, have also gone by the wayside. Moffat has steadfastly refused to resurrect characters from the previous administration, opting instead for his own original characters only. This is why neither Rory, nor River, nor Clara were the Master before. And it is also why Danny Pink, Missy, and the Doctor are not the Master now. As long as Moffat is running the show, characters like the Master, Captain Jack, Donna, and others will not be appearing in any Doctor Who episodes.