11 Times Doctor Who Reinvented Itself

In some ways, The Power of the Daleks changed the least out of all the episodes on this list. Coming in the middle of the fourth season, the story featured the same companions, the same TARDIS, and the same opening credits and musical theme. Even the threat of the adventure was the series' most iconic and familiar monster.

But what it did change was the Doctor. Nowadays, this is par for the course and something fans even get excited about, but back then, nobody was expecting it. But when William Hartnell's failing health made continuing in the show unlikely, the producers opted to do something a bit radical and to replace him. They did this not by bringing in a new character, but changing the Doctor himself. The completely dissimilar Patrick Troughton took on the role, making no effort whatsoever to try to make his Doctor's persona anything like his predecessor.

It was a massive gamble and a tremendous shift to the series people were familiar with. It completely altered the status quo of the show, and made Doctor Who a program that would never be the same again.