Reindeer

Reindeer were a mammalian species of the deer family, often associated with Santa Claus.

The Doctor, his companions and acquaintances occasionally encountered reindeer — and, indeed, Santa Claus himself. Once, Santa sent a sleigh pulled by reindeer to the First Doctor, John and Gillian to take them to his house. (TVC: A Christmas Story) On another occasion, the Third Doctor and Sarah Jane met St Nick on a New York estate — a meeting witnessed by Clement C. Moore. (ST: A Visit from Saint Nicholas)

Behind the scenes

 * A reindeer was a "special guest" in several short, non-canonical promotional videos produced for BBC One in 2009 for broadcast at Christmas of that year. The spots feature David Tennant, in costume and in character as the Tenth Doctor, cavorting in a snow-covered forest with the TARDIS and a reindeer. In the longest video of the promotion, the Doctor hooks several reindeer up to the TARDIS, and they take flight (suggesting they are flying reindeer like those used by Santa Claus). Two short "sting" promos of about ten seconds each show a single reindeer wandering outside the TARDIS.