After five decades of adventures in time and space, Doctor Who has a lot of history to celebrate, and the Day of the Doctor makes full use of that weird and complicated back-story to mark the 50th anniversary, while still looking to the future.
A movie-length love letter to all things Who, The Day of the Doctor appeared on TV screens all around the world simultaneously over the weekend, with special 3D cinema screenings that sold out weeks ago.
It featured the return of David Tennant - still the most popular Doctor by far, according to a recent Doctor Who Magazine poll - and a previously unknown Doctor played by John Hurt.
The story sees the three versions of the same Time Lord team up - after the requisite bickering - to overcome yet another invasion of Earth by slimy, sucker-covered monsters, saving the world with wit and cleverness.
Like many Doctor Who adventures, it's an episode full of cracking one-liners, bonkers science and surprising emotional depth. But as a special celebration episode, there are also several big, epic moments, and some shattering revelations.
Most notably, the episode shows the terror of the Time War - the great and final war between the Time Lords and the Daleks. While it has been hanging like a great shadow over the series ever since it returned in the 21st century, head Who writer Steven Moffat finally opens up the "time-locked" war for the first time, and shows the terrible price the Doctor had to pay to end the carnage.
As the Doctor who takes on the responsibility, Hurt is excellent, with the pain the war causes to his soul showing on his lined face, while still getting in a few good one-liners at the expense of his successors.
Tennant remains as dashing as ever as Doctor No. 10, easily returning to the role and highlighting the surprisingly large differences between his Doctor and the current bloke.
Matt Smith also holds up his end as that contemporary version of the Doctor, once again disguising the heavy weight of responsibility that sits on his shoulders with some shameless mugging (and fez-wearing).
These three are the latest to take on the celebrated role, but there are shout-outs to all the previous Doctors and the eras they represent, and plenty to remind the viewer of the show's twisting and turning heritage, from an opening featuring the original 1960s credits to a final shot of pure adoration for all the Doctors.
But it's also a celebration of all the adventures yet to come. The show has the tiniest glimpse of the immediate future for the series, which is apt because the Day of the Doctor has now come and gone, but there are still plenty more days to come for Doctor Who.
What: Doctor Who: The Day of the Doctor
Where: Prime, 9am global simulcast, Sunday, November 25