The Day of the Doctor, on BBC One (UK)
A.V. Club; BBC; Council of Geeks; IMDb; TV Tropes; Wikia; Wikipedia
streaming sites: Amazon; Google Play; iTunes; Vudu

This aired on November 23, 2013, the 50th anniversary of Doctor Who. But I didn't see it until July of 2018. It was preceded by a couple of online prequels. And it takes place after series 7 of the reboot of Doctor Who. Clara is now an English teacher at Coal Hill School, and one day she gets a message from the 11th Doctor. She immediately goes to see him, but instead of the two of them just going off on a random adventure... the TARDIS gets skylifted by UNIT, to deal with a new problem, which is explained to them by Kate Stewart. (There's also a scientist named Osgood, who wears a scarf similar to that of the Fourth Doctor- albeit shorter- and who uses an inhaler. I thought she was pretty great.) Anyway... some beings have escaped from some Gallifreyan paintings that UNIT somehow had possession of. And these beings turn out to be Zygons, who can shapeshift. Meanwhile, the Tenth Doctor is in 1562 England, cavorting with Queen Elizabeth I, but a Zygon soon shows up to replace her. Also meanwhile, the War Doctor (John Hurt) is about to use a doomsday weapon to destroy both the Time Lords and the Daleks, to end the Time War. The weapon (called "the Moment") has developed a consciousness, which takes on the form of Rose Tyler/Bad Wolf (Billie Piper), to help the War Doctor decide what he should do. (Of course this character is totally new and has its own personality, which I found absolutely delightful.) And... the three Doctors end up being brought together. And... it's really sort of hard to explain. Plus, I don't want to spoil anything. But they find different ways of dealing with the situation in 2013 England, and the situation on Gallifrey. (The situation in 1562 rather resolves itself.)

And... yeah, I guess that's all I want to say, except that... this special could change everything. Well, not everything, exactly. I mean, it could keep everything that's happened since the reboot began in 2005 unchanged, while simultaneously establishing a way for one particular thing of monumental consequence to be changed, in a very clever way. Anyway, the whole thing is bloody brilliant. (And funny, and poignant, and exciting, and whatever else one might expect a Doctor Who story to be.) Oh, and Clara, as always, is awesome.

Followed by The Time of the Doctor