The annual Doctor Who Christmas Special is always a TV highlight, even more so than when there's a regeneration looming. This year's offering, "Twice Upon a Time," not only saw the departure of Peter Capaldi as the twelfth Doctor, but also Steven Moffat as showrunner. The special also stood out for one very major change; the incoming Doctor is a woman.
The brief but fabulously fun appearance of Jodie Whittaker aside, Capaldi's last episode of Doctor Who was poignant and filled with emotion. It also featured David Bradley as the first Doctor, who like the twelfth was trying to resist regeneration. We've seen this before, of course; David Tennant's Doctor was very anxious not to go, and Matt Smith's wasn't too happy about it, either. But Capaldi was actively trying to prevent the process from happening, and he successfully managed to delay it for quite some time before accepting the inevitable.
Regeneration started for Twelve at the end of Season 10 (after taking out the Cybermen), and he stated outright that he didn't want to change. Bill had been taken from him, Nardole was living on another planet, and the Doctor was alone and hurting. Yet, he still wanted to stay. That shows, as had often been the case during Season 10, that there is a human, more emotive side to the Doctor. He's alien, yes, but he's capable of feeling worried, scared, and apprehensive just like the rest of us.
The Doctor Actually Could Have Died (This Page)
The Doctor Actually Could Have Died - If He Chose It
So we know the current Doctor doesn't want to go, and neither does (or did) the First, but Twelve can't remember this fact, which seems strange. It's, of course, to maintain continuity, but does have some in-universe basing. While the Doctor certainly does remember things, events, and people from his past, he seemingly cannot recall meeting future incarnations of himself; it's set up in "The Day of the Doctor," when Eleven confirms that John Hurt's War Doctor won't remember the truth of his actions. So, if the first Doctor won't remember meeting Twelve, does that mean that Twelve has forgotten what it was like to be One?
No matter the science (or timey-wimey) behind all that, both men come to find some common ground. “We have a choice, either we change and go on, or we die as we are,” Twelve tells One, and we know, of course, what choice both versions will make. This isn't a clear-cut aspect, though; the Doctor has already confirmed (in Season 9) that if a Time Lord is injured badly, they will die instead of regenerate, so death can come to the Doctor and maybe, one day, it will. For now, though, there's a regeneration on the cards.
Still, bearing in mind that death is something that can happen, it's fairly ominous that just before Capaldi gives his regeneration speech, he 'replies' to the TARDIS with "I suppose one more lifetime won’t kill anyone. Well, except me." Is that a clue of what's to come in the future? For one of the longest running TV series of all time, it seems doubtful for now, at least. However, Capaldi's final speech, directed to his incoming replacement, does contain several references to Doctor Who lore, including a nice nod to Capaldi himself, who has always been a lifelong Doctor Who fan.