(While this review does not contain major spoilers or specifics, it does talk about officially released details and some minor things may be given away.  It also draws your attention to hints in the episode. Read at your own discretion.)

Doctor Who returns for its now traditional Christmas Special. A strange man crashlands on Clara's roof, The Doctor returns and the two are soon reunited. Oh, and there's a north-pole expedition in danger. But...Santa! We get to find out who he is after waiting since Death in Heaven, the answer to which would have impossible without upsetting some people in some way.

But don't let Santa's presence screw with your expectations. While the episode may start on a fun note with Santa's one-liners, flying reindeer and a dance sequence, the Christmas special still contains some very dark threads from series 8, mostly on the incredibly depressing side, despite the astonishingly low body count. Luckily, the majority of these should fly over children's, and anyone who's not paying the utmost attention's, heads.

It's impossible to say much about this story without giving away or strongly hinting to the central plot, however the entire episode feels very much like they ran out of ideas and watched a few movies, and just slammed it all together unashamedly, even directly referencing the movie Alien. Surprisingly, however, it does actually work. Just.
To enjoy the plot to the fullest, this episode cannot be taken too seriously and must be viewed in light of the season. Despite this, the episode is well paced and provides plenty of entertaining one-liners to keep the episode fun and not too cumbersome. There's also a massive amount of references in here, from My Little Pony to Game of Thrones to the traditional festive Die Hard movie.

We also get some really good scenes between The Doctor and Clara and it can be very clearly seen that the loss of Danny Pink is still massively affecting her, which is woven into the plot very well. The closing scene between the pair in Death in Heaven, where they both lie to each other for each other's good, is addressed, yes, but as can be expected, not much can be made of it. It's obvious what happened to both the viewers and the characters so Moffat made the right choice by not focusing on it and moving swiftly on. Don't expect anything to actually come from it.
Likewise, we also find out definitively by the end of the episode whether Clara is staying or leaving. While we're not allowed to reveal it, I will say that I dislike how boring the cliffhanger turned out to be and how it was completely predictable.
Despite the issues and the lack of contact I have with the writing in this episode, Capaldi and Coleman, as usual, make the rather rough material they are given work incredibly.

Nick Frost is easily at the forefront of the guest cast, even getting a clunkily-placed title credit, and he plays the role wonderfully, mainly full of laughs and a bit of fun. Just a joy to watch. He's the Anti-Capaldi on the darkness line, although he does have a dark moment near the start that sent shivers down my spine.

The two elves, Nathan McMullen and Dan Starkey, added some amusing humour but they were only there to avoid the question of Santa being on his own.

The base's survivors were much better written, with Faye Marsay's Shona, Natalie Gumede's Ashley, Maureen Beattie's Bellows all receiving some rather well written back-story, given time restraints, and the acting was excellent.
Sadly, Patrick Troughton's children have had a pretty tough time with their Doctor Who characters between this episode and Midnight. Michael Troughton's Albert is also a professor who the show also tries to come off as a jerk, while providing very little story to. Disappointing.

Soundtrack wise, we get to hear our favourite theme from series 8 again among a few other themes, with few beautiful pieces.

Finally, the direction, CGI and set dressing of this episode is my favourite part of the episode. The episode is visually stunning, eerie and well edited. The fairly small number of locations works out very well as they are remade to look like a few different times, with a different feel. The CGI looked to be pretty good, however the low resolution preview wasn't very clear.

Overall, the episode feels like a lacklustre filler episode that adequately does its job, perhaps due to the big build-up that results in little, which is mainly the fault of the preceding episode's cliffhanger. This episode would work well binge-watched with the rest of the series later. It's neither the best or the worst, but it'll provide a decent amount of entertainment for the holidays. 6/10.

Last Christmas premieres on BBC One, Christmas Day at 6:15pm