Cobblemouse

A cobblemouse was an animal native to Gallifrey. When they matured, cobblemice grew wings.

The First Doctor once caught a cobblemouse in the mountain above the House of Lungbarrow. He let the cobblemouse loose in the House after his father and Mr Saldaamir ignored him. The cobblemouse interrupted the plans that they were making. (PROSE: Unnatural History)