10 Nu-Who Storylines That Doctor Who Spin-Off Media Did First
4. Changing Someone's Personal History
As well as Charles Dickens, Steven Moffat also borrowed from his own back catalogue when writing his first Christmas special. In the short story Continuity Errors, the Seventh Doctor meddles with the personal timeline of an obstructive librarian so that he can borrow an important book. The book can stop a war and avert a genocide, but this means nothing to the librarian.
The Doctor hops back and forth across her personal history, replacing one of her teachers, saving the life of her daughter from aliens, and becoming her friend. However, this friendship does not override her principles as a librarian and she still refuses him the book. While he eventually succeeds, the short story is emblematic of Steven Moffat's approach to the Doctor's character and motivations.
How can you trust someone who, if they wanted, could shape your history to suit them? Is he, as Moffat asks in the story a "Nice Guy or Utter Bastard"? That's basically the whole premise of Peter Capaldi's first series!
The tale is recounted in a lecture at the Luna University, at which a young Professor River Song would become a student. The planet-sized library in which Continuity Errors is set also influenced her introductory 2-parter Silence in the Library/Forest of the Dead.