History Recap / DoctorWho2017CSTwiceUponATime

* TheBusCameBack: The episode trailer reveals that Pearl Mackie as Bill will be in the episode, Polly will appear with the First Doctor, and we'll see the interior of the First Doctor's TARDIS, as well as the original police box design from the start of the show.

** What is the nature of the moment where TimeStandsStill, and who is the Captain they encounter there?

** As in a previous Twelfth Doctor ChristmasEpisode, "Last Christmas", he is reunited with his most recent companion just after they seemed to have parted ways forever, with neither knowing the truth about the other's situation.

* WhamShot:

** The reveal of Creator/MarkGatiss' role is presented this way in the trailer.
** Bill returns.

* The first multi-Doctor episode since "The Day of the Doctor", featuring Creator/DavidBradley as the First Doctor, and

* The first time the original TARDIS police box design from 1963 is seen in the main series, and the second time the original TARDIS interior appeared in the main series, after "[[Recap/DoctorWhoS35E12HellBent Hell Bent]]".

* RetCon: When "The Tenth Planet" aired, the term "regeneration" hadn't even been coined yet and the writers were quietly and vaguely trying to describe what happened to make the Doctor change appearance as though he just got younger and was still the same, while simply looking for an excuse to write Hartnell out and pussyfoot away from the issue. Now that regeneration has solidified as a concept in ''Doctor Who'', the issue is approached more directly with the First Doctor and Twelfth Doctor openly discussing that they don't want to "regenerate" as opposed to merely "change" and the last moments of the First Doctor are treated with more eloquence and grandeur by showing [[DoNotGoGentle he had one last thing to do before his time was up and refused to go quietly.]]

* The first time the original TARDIS police box design from 1963 is seen in the main series.

* FlashbackWithTheOtherDarrin: The events of the "[[Recap/DoctorWhoS4E2TheTenthPlanet The Tenth Planet]]" are seen, this time with new actors to play the Doctor and Polly, instead of William Hartnell and Anneke Wills.

* LighterAndSofter: As a deliberate contrast to "World Enough and Time"/"The Doctor Falls", which put the Doctor and his companions (especially Bill) through the wringer, saw Missy's HeelFaceTurn stopped in its tracks by her previous self, and climaxed with the Doctor's HeroicSacrifice followed by his desperation to '''just die''', this story is promised by Moffat to be a hopeful, uplifting, funny end to the Twelfth Doctor's saga. (One event confirmed by the trailer, in fact, is a reunion for the Doctor and Bill, who each believed the other to have died as a result of the previous story's events.) This follows in the footsteps of Twelve's previous Christmas episodes. "Last Christmas" and "The Husbands of River Song" were ultimately joyous codas to the extremely {{Bittersweet Ending}}s of Series 8 and 9 and "The Return of Doctor Mysterio" also looked to the future with hope even in the face of sorrow.

* RetCon: When "The Tenth Planet" aired, the term "regeneration" hadn't even been coined yet and the writers were quietly and vaguely trying to describe what happened to make the Doctor change appearance as though he just got younger and was still the same and were simply looking for an excuse to write Hartnell out and pussyfoot away from the issue. Now that regeneration has solidified as a concept in ''Doctor Who'', the issue is approached more directly with the First Doctor and Twelfth Doctor openly discussing that they don't want to "regenerate" as opposed to merely "change" and the last moments of the First Doctor are treated with more eloquence and grandeur by showing [[DoNotGoGentle he had one last thing to do before his time was up and refused to go quietly.]]

* MeetYourEarlyInstallmentWeirdness: The Twelfth Doctor meets the First! Though, considering the Doctor, no installment of his is ever non-weird. The same goes for the TARDIS, which is seen in its original smaller and blocky shape as opposed to the much larger, bluer, and modernized one it now is (a few cosmetic changes like the windows, the lantern shape and the typeface of the box are apparent.

* TheBusCameBack: The episode trailer reveals that Pearl Mackie as Bill will be in the episode, Polly will appear with the First Doctor, and we'll see the interior of the First Doctor's TARDIS.

* MeetYourEarlyInstallmentWeirdness: The Twelfth Doctor meets the First! Though, considering the Doctor, no installment of his is ever non-weird.

* RetCon: When "The Tenth Planet" aired, the term "regeneration" hadn't even been coined yet and the writers were quietly and vaguely trying to describe what happened to make the Doctor change appearance as though he just got younger and was still the same. Now that regeneration has solidified as a concept in ''Doctor Who'', the issue is approached more directly with the First Doctor and Twelfth Doctor openly discussing that they don't want to "regenerate" as opposed to merely "change".

* MeaningfulName: "Twice Upon A Time" as in revisiting a previous adventure with a past Doctor and both Doctors experience its events firsthand.

* OnceMoreWithClarity: We see how the Twelfth Doctor was involved in "The Tenth Planet."

* MeaningfulTitle: "Twice Upon A Time" as in revisiting a previous adventure with a past Doctor and both Doctors experience its events firsthand.

* AndStarring: The billing of [[spoiler: Pearl Mackie]] is presented this way in the first trailer.

* TheBusCameBack: The episode trailer reveals that [[spoiler:Pearl Mackie as Bill]] will be in the episode, Polly will appear with the First Doctor, and we'll see the interior of the First Doctor's TARDIS.

** As in a previous Twelfth Doctor ChristmasEpisode, [[spoiler: "Last Christmas", he is reunited with his most recent companion just after they seemed to have parted ways forever, with neither knowing the truth about the other's situation]].

* LighterAndSofter: As a deliberate contrast to "World Enough and Time"/"The Doctor Falls", which put the Doctor and his companions (especially Bill) through the wringer, saw Missy's HeelFaceTurn stopped in its tracks by her previous self, and climaxed with the Doctor's HeroicSacrifice followed by his desperation to '''just die''', this story is promised by Moffat to be a hopeful, uplifting, funny end to the Twelfth Doctor's saga. (One event confirmed by the trailer, in fact, is [[spoiler: a reunion for the Doctor and Bill, who each believed the other to have died as a result of the previous story's events]].) This follows in the footsteps of Twelve's previous Christmas episodes. "Last Christmas" and "The Husbands of River Song" were ultimately joyous codas to the extremely {{Bittersweet Ending}}s of Series 8 and 9 and "The Return of Doctor Mysterio" also looked to the future with hope even in the face of sorrow.

Aside from his dearest, most loyal companion of all, the TARDIS. Bill and Heather having returned the Doctor to her, "Sexy" will not let him give up on life -- and the universe that needs him -- so easily. Of her own volition, it has brought the Doctor to Antarctica [[Recap/DoctorWhoS4E2TheTenthPlanet at the time and place]] where his very first incarnation was wearing a bit thin and also resisting the prospect of change.

** [[Recap/DoctorWhoS30E1718TheEndOfTime Once]] [[Recap/DoctorWho2013CSTheTimeOfTheDoctor again]], the Doctor's regeneration story has the word "time" in its title.

* TheBusCameBack: The episode trailer reveals that [[spoiler:Pearl Mackie as Bill]] will be in the episode.

* LighterAndSofter: As a deliberate contrast to "World Enough and Time"/"The Doctor Falls", which put the Doctor and his companions (especially Bill) through the wringer, saw Missy's HeelFaceTurn stopped in its tracks by her previous self, and climaxed with the Doctor's HeroicSacrifice followed by his desperation to '''just die''', this story is promised by Moffat to be a hopeful, uplifting, funny end to the Twelfth Doctor's saga. This follows in the footsteps of Twelve's previous Christmas episodes. "Last Christmas" and "The Husbands of River Song" were ultimately joyous codas to the extremely {{Bittersweet Ending}}s of Series 8 and 9 and "The Return of Doctor Mysterio" also looked to the future with hope even in the face of sorrow.

** What is the nature of the moment where TimeStandsStill?

* WinterWarfare: The Doctors meet the Captain at a front line that's covered in snow, at a moment frozen in time to boot.

* DrivingQuestion: The Twelfth Doctor is ''tired'' of life, loss, and change -- what will he find WorthLivingFor via encountering his previous self?

** At the end of an emotional confrontation with one of his great enemies and after an ensuing HeroicSacrifice, a bitter, cynical, middle-aged Doctor regenerates into a new, young incarnation with bright brown eyes and a charming smile. This change - marking the passing of the torch from a well-known veteran actor to a total dark horse - leaves fans uncertain, but mostly hopeful. [[Recap/DoctorWhoS27E13ThePartingOfTheWays Here we go again.]]
* LighterAndSofter: As a deliberate contrast to "World Enough and Time"/"The Doctor Falls", which put the Doctor and his companions (especially Bill) through the wringer, saw Missy's HeelFaceTurn stopped in its tracks by her previous self, and climaxed with the Doctor's HeroicSacrifice followed by his desperation to ''just die'', this story is promised by Moffat to be a hopeful, uplifting, funny end to the Twelfth Doctor's saga. This follows in the footsteps of Twelve's previous Christmas episodes. "Last Christmas" and "The Husbands of River Song" were ultimately joyous codas to the extremely {{Bittersweet Ending}}s of Series 8 and 9 and "The Return of Doctor Mysterio" also looked to the future with hope even in the face of sorrow.

* WinterWarfare: The Doctors meet at the front line when it's covered in snow.
* WorthLivingFor: The Twelfth Doctor has just been put through the wringer and barely managed a DisneyDeath. He doesn't have any companions with him, and it can be assumed he believes Bill was KilledOffForReal. If he regenerates, he'll lose the personality and appearance he's grown to be happy with and have to adjust to a new one all over again, and owing to his perpetual ChronicHeroSyndrome he'll face more dangers, more successes but also failures, and more friendships with mere mortals that will inevitably end in loss. With no family or homeworld on top of all this, he's simply ready to die for good -- but over the course of this surprise adventure he'll find a reason to keep on living, even in a new form.

* It's also the first time in the revival era - and only the second time ''ever'' - that a previously-seen [[TheNthDoctor incarnation of the Doctor]] has been played by a [[TheOtherDarrin replacement actor]] in a major, episode-long appearance, with David Bradley replacing Richard Hurndall from "[[Recap/DoctorWho20thASTheFiveDoctors The Five Doctors]]" after Hurndall himself replaced the ''first'' First Doctor, Creator/WilliamHartnell, for ''that'' one-off multi-Doctor story.

Aside from his dearest, most loyal companion of all, the TARDIS. Bill and Heather having returned the Doctor to her, "Sexy" will not let him give up on life -- and the universe that needs him so badly -- so easily. Of her own volition, it has brought the Doctor to Antarctica [[Recap/DoctorWhoS4E2TheTenthPlanet at the time and place]] where his very first incarnation was wearing a bit thin and also resisting the prospect of change.

Two incarnations of one soul, so similar yet so different, have crossed paths, and together they will embark upon their respective last journeys, upon which they will (re)learn to embrace the prospect of change and renewal. At the end of the First Doctor's path, he will change for the very first time; at the end of the Twelfth's he will change in a way he never has before...

And who and what else might be changed for their journeys?

* TheBusCameBack: The episode trailer reveals that [[spoiler:Pearl Mackie as Bill]] will be in the episode.

* TimeStandsStill: The battleground freezes, both literally and... literally, at the appearance of the Doctors.