Mouse

A mouse was a type of mammal (AUDIO: The Sleeping Blood) known to be found on Earth (TV: Planet of Giants, PROSE: The Time Travellers, et al.) and Gallifrey. (TV: Time and the Rani)

From Earth
Professor George Litefoot had pet mice as a child. (AUDIO: Encore of the Scorchies)

In 1879, Rose-the-Cat piloted the TARDIS to Paris, France, where she found a mouse. (COMIC: A Rose by Any Other Name)

Queen Victoria had a problem with mice at Balmoral Castle. (AUDIO: Fortitude)

When the Tenth Doctor landed in Paws 'N' Claws, they defeated Cybermen. However when he and Rose went to defeat the Cybermice (converted mice), a mouse which looked like the Tenth Doctor was already stopping them. (COMIC: Untitled)

In Prague, used the time winds to bring a dead mouse back to life and accelerate its evolution by millions of years into a humanoid form, which he planned to use as a new host body for himself, but the Seventh Doctor defeated the Master's plan. (PROSE: Omegamorphosis)

In the year 4000, Froyn and Rhynmal intended to test their new long-range teleportation system by sending two lab mice to Mira. These were later exterminated by Daleks. (TV: The Daleks' Master Plan)

Bertram brought his pet mice on board the Karsudan. During his long sleep, the mice multiplied and infested the ship, damaging many of its systems. The cog on the ship fed on the mice. (PROSE: All Snug in Their Beds)

Elsewhere
On Gallifrey, a mouse was enlarged by during an experiment. The giant-sized mouse ate the Lord President's pet cat and bit the President himself, which resulted in the Rani's expulsion from Gallifrey. (TV: The Mark of the Rani)

The Ninth Doctor claimed that there was a planet which had talking mice. (PROSE: Winner Takes All)

Behind the scenes

 * Jon Pertwee acquired a field mouse as a temporary pet during a break in the location filming for The Mutants at Stone House Farm in Frindsbury, Kent. He named the mouse Solos, after the planet featured in the story.