Perhaps more than any other show, Doctor Who has thrived on constant evolution.
This is most obvious with the Doctor's ever-changing characterization, but that is only one of many elements that have been adjusted repeatedly. Over its 50+ years of existence, nearly every aspect of Doctor Who has gone through multiple variations. Most of the audience has come not only to accept that the necessity of this, but to anticipate and embrace each new development.
Indeed, in modern times, the debut of a new lead actor is a media event. Fans eagerly devour details of what the new Doctor will be like, how they will dress, who the companions will be, what the TARDIS will look like, how the theme music will be arranged...and generally what the series will be like going forward.
What has rarely shifted is the premise itself: the Doctor, a time-traveling alien, wanders through the universe, fighting monsters and making friends. But the way that story has been told has been in a constant flux, almost from the very beginning of the program.
Here are the top eleven times Doctor Who reinvented itself.
11. The Timeless Children (2020)
First up is the most recent item on this list--in fact, it's from the last episode of the latest season of the show. However, it represents such a huge adjustment to the series' backstory, it can't be ignored.
After some slight hints that were strewn through Jodie Whittaker's tenure on the program, it was revealed that everything the Doctor has understood about her life is a lie. Rather than being an "ordinary" Gallifreyan, she is actually an ancient creature of unknown origin, known only as the Timeless Child, whose apparently natural ability to regenerate was harvested in order to create the Time Lords as we know them.
It's a potentially seismic shift to the status quo of the program--perhaps the largest that we've ever been presented with. To say that fans have been divided by this twist is an understatement.
However, in spite of its significance, the revelation of the Timeless Child remains low on this countdown simply because it's still too recent to know how much of a genuine re-imagining of the series that it will come to represent.