The Witches by Roald Dalh

Mice are, clearly, a very important part of The Witches: the climax of Dahl's story is almost 100 witches turning into a mass of brown mice before a crowd of onlookers. Mice are first mentioned when the boy uses them as a reference point in a description of his grandmother; he says that she filled up her armchair so much that even a mouse couldn't fit in it with her. After that, as the boy and the grandmother's stay at the hotel approaches, she buys him two white mice that he names William and Mary and starts to train to do tricks. While the boy exerts control over these mice, he is always kind to them and is never scared; as a rule, the adults in Dahl's story are scared of mice and children are not, though the grandmother is a notable exception to this rule. In the end, Bruno, the boy, and all of the witches are turned into mice. The boy contemplates whether life would be better as a person or a mouse, and decides that life as a mouse may be better because there is no school and no wars, a deep, insightful moment for such a young child regarding significant and age-old human problems.