Mountain goat

A mountain goat was a particular kind of goat, whose sure-footedness made it particularly adept at climbing mountains. When having to climb an incline with the Tenth Doctor and Mohandas Gandhi in India in 1947, Donna Noble struggled in comparison and claimed, "We're not all descended from mountain goats, you know." As it turned out, the inhabitants of the planet Istervaal were descended from mountain goats. (PROSE: Ghosts of India)

In 1055 Northumbria, the First Doctor refused to climb a cliff, saying that he was not a mountain goat and preferred walking to any day, and that he hated climbing. (TV: "The Watcher")