Mouse

Mouse is a rarely used creature type which first appeared on tokens in Throne of Eldraine. It depicts small rodents with a pointed snout, relatively large ears and eyes, and a long tail.

This creature type came into being only because the Enchanted Carriage needed white Mice for flavor. R&D talked about the card making Rat or Squirrel tokens, but ultimately decided in favor of mice.

The Mouse type returned as a non-token creature in Zendikar Rising with Canyon Jerboa.