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. (TVC: A Christmas Story) Much later in the Doctor's life, the Visual Recognition System identified a drawing of a Krafayis as a polar bear. (DW: Vincent and the Doctor)