In common fan parlance, a multi-Doctor story is one that involves more than one incarnation of the Doctor. Typically, although not necessarily, such tales are reserved for anniversary and/or charity events. The term is not usually applied to stories like The Almost People which involves a doppelgänger, or Father's Day, which has multiple instances of a single incarnation. Despite this the Doctor Who team published an article in which they listed Day of the Daleks as one of their favourite multi-Doctor stories, citing the scene in part one in which the Third Doctor and Jo meet future versions of themselves.
They are exceedingly rare on television and audio, but much more common in short stories and comics.
Multi-Doctor stories include:
- Main article: List of multi-Doctor stories
Many aspects of the multi-Doctor story have been explored over the years in many different forms. The Multi-Doctor story bases itself in the bending of the Laws of Time, as the Doctor is explicitly disallowed from crossing their own time-stream.
A contentious topic for fans (and for a time, only fans) was if the characters featured in multi-Doctor stories would actually be allowed to remember the events of the story afterwards. If, for instance, the Second Doctor did not forget the events of The Three Doctors, then it would make little sense for the Third Doctor to not also remember meeting himself. Many fans speculated that this meant that the Time Lords simply wiped the Second and First Doctors' memories afterwards. This some somewhat supported by such stories as The Empire of Glass and Briefly Noted.
Writers at the time, however, were not concerned with this continuity point. Indeed, in the televised story The Five Doctors the first, second, and third incarnations of the Doctors consistently speak as if they recall the events of The Three Doctors. On one occasion, the Second Doctor directly mentions fighting Omega to the Brigadier, and upon meeting his third incarnation, the First Doctor asks where the "little fellow" is.
An early script for Dimensions in Time featured a scene where Jamie McCrimmon would suddenly find himself next to the Sixth Doctor, leading Jamie to recognise him from their encounter in The Two Doctors. This scene was cut after Frazer Hines realised that he would not be able to meet the schedule of production.
One of the most notable examples of versions of the Doctor remembering the events of the story was in 2007's Time Crash, where a central plot point to the Fifth and Tenth Doctors' survival in the story is that the Tenth Doctor remembers seeing himself save the day from the point-of-view of the Fifth Doctor.
Since these stories, most mainstream and secondary stories have to come to accept the idea that characters lose their memories after the events of Multi-Doctor stories. The Day of the Doctor features the realisation that the Tenth Doctor and the War incarnation of the Doctor will both forget the events of the story in due time. Four Doctors expanded on this, stating that in multi-Doctor events, all but the final incarnation of the Doctor will forget about the story's taking place. Their companions, however, will remember. Later stories contradicted this, with Lady of the Blue Box suggesting that Gabby barely remembers the events of Four Doctors and The Heralds of Destruction implying that even the Third Doctor had all-but-forgotten the events of The Three Doctors.
In his novelisation for The Day of the Doctor, Steven Moffat expanded on his original memory loss concept, stating that the later incarnations present remember the events from the point of view of the earlier ones as they catch up to that moment again, and later forget again if an incarnation from even further in the future is also present.
Regarding the Eleventh Doctor's meeting with the Curator in The Day of the Doctor, Steven Moffat confirmed in DWM 487 that the Curator is intended to be a future incarnation of the Doctor and suggests that, just as the War and Tenth Doctors retain no memory of the events of The Day of the Doctor, the Eleventh Doctor would not remember the specifics of his conversation with the Curator but will leave the Under Gallery "with the strange, groundless conviction that Gallifrey is still out there". This was reflected in The Time of the Doctor in the Eleventh Doctor's uncertainty regarding whether Gallifrey was actually saved.
Like most things in the impossibly large spectrum of Doctor Who content, deciding which of these accounts hold true is up to each and every fan to decide.