Polar bear

Polar bears were a type of bear typified by their all-white pelts, and their proclivity for living in cold climates. During a mission for Santa Claus in snowy conditions, the First Doctor encountered and was menaced by a polar bear. He was rescued by John and Gillian, who used the Doctor's "magic box" to miniaturise the bear. (COMIC: A Christmas Story)

As the Eleventh Doctor attempted to use the Visual Recognition System to determine the species of a drawing of a Krafayis, it offered a polar bear as one of the incorrect identifications. (TV: Vincent and the Doctor)

The Soviet submarine, the Firebird, kept a cattle prod on board for when they encountered polar bears. (TV: Cold War)

In an alternate timeline, a mounted polar bear was one of the exhibits in the National Museum. (TV: The Big Bang)