John Hurt
From Tardis Wiki, the free Doctor Who reference
John Hurt played an unknown incarnation of the Doctor in TV: The Name of the Doctor. It is suspected that he will play a previously forgotten incarnation of the Doctor, placed somewhere between the Eighth Doctor and the Ninth Doctor[1].
Within the Doctor Who universe
John Hurt exists as an individual within the Doctor Who universe. In TV: Greeks Bearing Gifts, Toshiko Sato compared the body of a dead soldier with his heart ripped out to "that bit in Alien where that thing bursts out of John Hurt."