Inevitably unique to Earth unless you count the likes of Omega and Davros, the “celebrity historical” has the Doctor bumping into someone known from the history books, to the varied delight and outrage of historians and the like.
As far as I know, the Doctor has never met any of the following on TV. Feel free to correct me if/when I’m wrong.
Joan Of Arc
A sample PC in one of FASA’s Doctor Who adventures (yes, really) Joan could appear as, for example, a true seer being lead by visions of two possible futures. Whatever the case, European history and the history of world colonisation that follows pivots around her life.
Pierino da Vinci
The nephew of Leonardo showed signs of genius on a level with his uncle's before he died in his early twenties. How, and why?
A self-proclaimed sorceress who nearly brought down the court of France. What was she really capable of?
“Do you think to shock me, sir? That I do not know that this is a benighted world, haunted by terrors beyond the wit of man?”
(Edit: He’s met her in the audios and in the kids’ comics.)
The daughter of Lord Byron and the first computer programmer, a Renaissance woman in every respect, one of the most accomplished people in history... Would the Doctor like her or what?
A key, controversial figure in African history, a fierce leader who changed a nation and a continent, subject of legends and conflicting accounts in his own lifetime and beyond.
A leader of the October Revolution and the Russian Civil War, squeezed out of power by Stalin when Lenin thought him the better choice to succeed him, murdered in exile over a decade later. Had things turned out differently, the last century of the history of eastern Europe might change beyond all recognition. How would he feel knowing that? How would he react to what Communism became under Stalin - or to other examples of extremism, like the Daleks or the Cybermen?
J.R.R. Tolkien, C.S. Lewis and Charles Williams
Academics with a sideline in imagining unknown histories filled with heroes and monsters, other worlds accessed by opening secret doors, and inhuman visitations on the present day. How would the Inklings react to meeting a very real dragon?
(Edit: the first two cameo’ed in the DWM 2010 Christmas Special comic strip.)
Before coining the term “artificial intelligence” he was already vital in the British war effort and could have gone on to greater things if not for how history played out.
The first man in outer space, just two and a half years before Doctor Who began but now certainly qualifying as an historic figure, and certainly of interest to those who would like to change the history of human space exploration.
Russell T Davies had an idea to have her appear as herself in a Christmas special, a celebrity historical set in the present. A mad idea, but...