Cinderella (Disney film)/WMG

The anthropomorphic traits of the mice around Cinderella's house are a result of the Fairy Godmother's magic.
It was something she [the Fairy Godmother] set up so that the poor, practically enslaved girl wouldn't be lonely.

The anthropomorphic mice are the ancestors of all the mice in the various Mouse World movies.
Cinderella gave clothest to the mice and taught them to talk. Given the high reproduction rate of mice, the descendants of these mice spread all over the Earth, probably also teaching the other mice to dress and talk. By the end of the 19th century, they had a whole kingdom in England, and communities in Russia. By the late 20th century, they had a global society protecting humans.