Hamsters were Earth mammals, often kept by humans as pets. Dougal Dunnock owned one, which he tried to breed with Mervin the Missing Link. (PROSE: The Last Dodo)
In her youth, Ace was the "hamster monitor" in the classroom run by Miss Marshall. (PROSE: Legacy) The Fourth Doctor once reproached K9 for his slow progress in cutting through a wall with his laser by saying that "a hamster with a blunt penknife" could do it more quickly. (TV: The Androids of Tara)
