The one where the first three Doctors team up...
Doctor Who celebrated its tenth anniversary a whole 11 months before the actual anniversary, because the tenth season started in December 1972. Would it have been wiser to celebrate the anniversary at the start of Season 11, which started in December 1973? Or would that have been too late?
The idea of having more than one Doctor at a time starts here. There'd only been subtle hints and reminders of "earlier Doctors" before now (a glimpse of Hartnell in The Power of the Daleks, and the first two Doctors seen during the Dalek mind scan in Day of the Daleks), but this story was the first to acknowledge properly that there had been earlier Doctors - other actors - and to joyfully bring them back! Now that's pretty damn exciting, isn't it?






