In the special, the alien time traveller the Doctor is reunited with his companion Clara Oswald as they try to save a North Pole science base from creatures called dream crabs that induce dream states whilst killing their victims, with the help of Santa Claus.

The Doctor and Clara arrive at a North Pole base where four of the crew in the infirmary are being devoured by Dream Crabs – blind aliens which induce dreams on their intended victims as a distraction whilst devouring the victims' brains and which use telepathy to see the surroundings of people thinking about a crab.

The affected personnel – manifestations of the Doctor, Clara, and the "scientists'" minds – attack and kill Professor Albert.

[1] In September 2014 announcements were made for a number of the guest cast, including Michael Troughton, Nick Frost, Nathan McMullen, Natalie Gumede and Faye Marsay.

[2][3] Coleman and lead writer Steven Moffat remained quiet on the issue and insisted that people watch the episode to see whether she would be continuing into the ninth series.

[7] Marsay's character of Shona was considered by Moffat to be Coleman's replacement as the companion for the ninth series, though nothing was fully formed.

Elements of Shona were later reworked into the character of Bill Potts, who was the companion when Coleman left after series nine.

[14] The scenes involving ice plains were filmed in a constructed set in RAF St Athan.

[16] A preview was shown during Children in Need which featured The Doctor, Clara, Nick Frost as Santa Claus, and Dan Starkey (who also plays Strax of the Paternoster Gang) and Nathan McMullen as elves.

[20] However, it received a total of 2.62 million viewers on BBC America, beating the previous record established by "The Time of the Doctor", and became the most watched episode of the revived series in the channel's history.

Club awarded the episode the highest grade of the site, finding the script "inordinately clever" in making a at-first-glance "fluffy, silly Christmas special" scary.

[25] Michael Hogan of The Daily Telegraph stated that it "had heart as well as head" with a festive special feel of "cockle-warming cosy glow".

[33] Writing for Digital Spy, Morgan Jeffery found the episode an "absolute cracker" that refused to be "light on substance".

[32] Simon Brew of Den of Geek heavily praised the episode and considered it an improvement over the previous Christmas special "The Time of the Doctor".

[38] Selected pieces of score from "Last Christmas", as composed by Murray Gold, were released on 18 May 2015 by Silva Screen Records as the third disc of the soundtrack covering series 8.