10 Biggest Events In Doctor Who That You Never Got To See
2. The Second Doctor's Regeneration
By the close of the War Games, the Doctor is put on trial by the Time Lords and forced to regenerate. The last shot of Patrick Troughton that the audience saw was the man twirling around in a circle, fading off into the black. The next time that the Doctor would be seen, Jon Pertwee would be stepping out of the TARDIS in full colour.
The War Games is a pivotal moment in Whovian history. It was the last serial produced in the 1960s, the last story for Troughton and the last featuring that incarnation of the TARDIS gang. It introduced the Time Lords and Gallifrey to the canon. It also introduced the idea that they held the Doctor as a criminal for breaking their laws of non-interference, though he successfully argues that evil must be fought.
The story closes with the Doctor being forced to regenerate, though this isn't shown. It is the only regeneration to date that has never been shown in any medium at all, with the Eighth Doctor finally receiving his big scene in The Night of the Doctor and the Ninth Doctor technically appearing in The Day of the Doctor.