Kangaroo

s were mammals common to Australia.

History
In 1979, a young Western Australian boy named Harvey met the Tenth Doctor soon after stumbling across a kangaroo with glowing eyes. It turned out that the animal had been affected by the recently-fallen Skylab. (PROSE: Bennelong Point)

On at least one adventure with the Eleventh Doctor, Abigail Pettigrew went to Uluru and was photographed in front of a kangaroo crossing sign. (TV: A Christmas Carol)

Kangaroos were among the animals on board the Ark in circa 10,000,000. (PROSE: The Ark)

One of Iris Wildthyme' future incarnations starred in a successful television series as well as several films. Her companion Panda only appeared in the pilot episode of the series before he was replaced by a kangaroo named Hoppy. (AUDIO: The Iris Wildthyme Appreciation Society)

Other references
Immediately after regeneration, the Seventh Doctor's brain was addled, and he unwittingly altered several common metaphors. He claimed that Melanie Bush had the "mind of a kangaroo" before she reminded him that people with great memories were said to have the "mind of an elephant." (TV: Time and the Rani)