Season 6B

Season 6b is a popular fan theory, used to explain continuity erros in The Five Doctors and The Two Doctors. The hypothetical season takes place between The War Games (Last serial of Season 6), and Spearhead from Space (first of Season 7). It is unknown if it is canon, but several spin-off material has been set during this time.

The Five Doctors
In the Five Doctors, The Second Doctor claims that Jamie McCrimmon and Zoe Heriot should not recognise himself or The Brigadier, as they had their memories wiped. This appears to contradict The War Games, where the doctor appeared to regenerate at the end. Since the Second Doctor would not be aware of the memory wipe if he was taken before The War Games, there is no easy way that he can know this, and still be the Second Doctor.1

The Two Doctors
The Two Doctors shows an aged Second Doctor travelling with Jamie on a mission for the Time Lords. However, Jamie was not aware of the Time Lrods untill The War Games (This was confrmed as an error by the writer). The aged appearance of the two actors also suggests it is after The War Games.

Season 6B
To account for these apparent discrepancies, Paul Cornell proposed the "Season 6B" theory, first published in the The Discontinuity Guide, by Cornell, Martin Day and Keith Topping. This hypothetical season took place off-camera between The War Games and Spearhead from Space, and had Troughton's Doctor working as an agent of the Time Lords, specifically their covert organization the Celestial Intervention Agency (the first actual mention of it was in Season 14's The Deadly Assassin, but in direct connection with the War Games trial), who granted him increased control over his TARDIS at the cost of his freedom. The Second Doctor who showed up in The Five Doctors came from this period, and was therefore aware of Jamie and Zoe's mindwipe.

During this time, the Second Doctor apparently regains Jamie and Victoria Waterfield (who is mentioned as being away studying in The Two Doctors) as companions, acquires a Stattenheim remote control device to summon his TARDIS, and undertakes the mission which was related in The Two Doctors. Eventually, either the Time Lords tire of keeping the Doctor on a leash, or the Doctor rebels and attempts to escape once more. This results in the exile which begins in Spearhead from Space. To explain why the Sixth Doctor does not remember his own past in The Two Doctors, it is also suggested that the Time Lords wiped the Second Doctor's memory of the events of Season 6B (the Third Doctor did claim significant memory loss in Spearhead).

Spin-off Material
Several spin-off material has been released covering this season.

PDA: World Game PDA: Players (with the Sixth Doctor) ST: Mother's Little Helper ST: Scientific Adviser ST: Reunion BFA: Fear of the Daleks (with Zoe)