Fledershrew

Fledershrews were a species of bat that were near extinction on their home planet. Fledershrews gnawed at the rafters of the House of Lungbarrow. (PROSE: Lungbarrow)

During his seventh and eighth incarnations, the Doctor allowed an entire colony of Fledershrews to live in his TARDIS. (AUDIO: Black and White, Nevermore, Relative Dimensions)

Shortly after the Doctor's granddaughter Susan Campbell and great-grandson Alex Campbell arrived in the TARDIS to celebrate Christmas with his eighth incarnation and Lucie Miller, the Fledershrews were all killed by the Blitzen fish. (AUDIO: Relative Dimensions)