2. The Five Doctors (1983)
Doctor Whos twentieth anniversary really set the standard for celebrating the programmes history with exhibitions, every story of Season 20 featuring a returning enemy, and The Five Doctors: a 90 minute special that saw the Doctors being taken out of time and deposited in the Death Zone (an abandoned gladiatorial arena on Gallifrey) to play the Game Of Rassilon and discover his secret of immortality. A more accurate title for this special would be The Three And A Half Doctors since Tom Baker refused to take part (a decision he now regrets) and, because William Hartnell had passed away in 1975, the role of the First Doctor was played by Richard Hurndall, who was cast for his resemblance to Hartnell. But despite that, its still a cracking story. The Five Doctors does exactly what its supposed to. It gathers together a large number of elements from Doctor Whos past and present, and uses them to tell a large scale story. As well as four Doctors; we get the Master, Daleks (Well, a Dalek), Cybermen, a Yeti, and a companion for each of the past Doctors with three more appearing as illusions. The Doctors are mainly operating solo with their respective companions as they attempt to reach the Tomb Of Rassilon at the centre of the Death Zone but once they join together for the climax, it really hits the mark since, once again, we see them working together and overcoming evil. On top of that, the final moment where the Doctor goes on the run from the Time Lords and observes Thats how it all began is the perfect way to not only end the story, but also to start the next step of Doctor Whos life.