Mice in Narnia did not always speak. Aslan gave speech to the mice after they had loosened the cords that the White Witch used to bind Aslan. There are only two notable mice mentioned in any detail in the Chronicles of Narnia.
Reepicheep is the Chief mouse and was knighted for his brave and dedicated service. Reepicheep one the most beloved characters in the Chronicles of Narnia was featured in the following volumes of the Chronicles of Narnia: Prince Caspian, The Voyage of the Dawn Treader, and The Last Battle.
Reepicheep has dark (almost black) fur. He stands about two feet tall, and walks on his hind legs. While voyaging to the end of the world on the Dawn Treader, Reepicheep decided to stay behind in Aslan’s country.
Peepiceek is the other notable mouse in Narnia, and was second in command of the Narnian mice. Later because of the absence of Reepicheep, Peepiceek became the leader of the Narnian mice.