Tussan's cat

Tussan's cat was a Gallifreyan cat and a key figure in early Gallifreyan history. A sophisticated, calculative creature with high ambitions, it was originally, as the only name recorded for it in the Scrolls of Gallifrey suggested, the pet of Tussan, the last Council Leader of the old Gallifreyan Council, and later became the advisor of Rassilon.

Biography
Cats being symbols of intelligence in Gallifreyan culture, Tussan's cat sat by his master Tussan on the Gallifreyan Council on the day Rassilon and Omega came to ask the Council to finance their time travel experiments. Seeking to insult Rassilon, Tussan decided to let his pet decide the answer. To Tussan's surprise and dismay, the cat, after an ostentatious yawn, answered that Gallifrey should in fact back Rassilon and Omega's time travel experiments.

Some time later, when Rassilon collapsed, dying, in the Council chamber from prolonged exposure to the Eye of Harmony, Tussan's cat leapt down and hissed in Rassilon's ear not to give up. This triggered Rassilon's first regeneration, the first regeneration of any person on the planet of Gallifrey. Rassilon soon used the mystique of his resurrection to overthrow Tussan and seize power; when he did so, Tussan's cat abandoned its old master and became Rassilon's pet, deciding it was meant for greater things than being the companion of a failed politician.

This set a tradition of Lord Presidents always having a pet intelligent cat. Pandad IV seemed to break this tradition, not getting a new cat after (PROSE: The Legacy of Gallifrey) his own quadrupedal companion was killed by the First Rani's giant mice; (TV: The Mark of the Rani) however, Flavia would eventually renew the tradition, getting a cat whom she named the Doctor. (PROSE: The Legacy of Gallifrey)