Mice are found in every world. Along with the Spider, Mice are the first enemies to be faced. They are first seen in World 1, in the first and second level. After that, they became regular enemies in all games.
They are the only enemies in the series that use guns that shoot out projectiles, which can make them tricky and annoying enemies to defeat, however, they are immobile.
Instead of moving around, mice stay where they are, and if you get near them, they will shoot at you with their weapon. The projectile that they shoot appears to be some sort of squiggle ball. It travels at the direction the mouse shoots at a medium-slow speed. This makes it possible to dodge or jump over projectiles, and even destroy them with weapons. In World 1, they only take one hit to defeat. In World 2 and World 1 Remix, they take two hits. In World 3, they take three hits.
In World 1 and its remakes, Mice appear as regular enemies along with Spiders,a nd one of the only enemies in the game. They are found in first two levels, mostly blocking player's path.
Similarly to World 1, they appear in all areas of the game, and they are secondary enemies, after Spiders.
In The Fancy Pants Adventures, and its PC version World 3, Mice are less frequent enemies due to more diverse types of other enemies. However, they are still dangerous and can appear at some unexpected places such as the Forgotten Island. In this adventure they appear mostly in the Squiggleville, especially its industrialized outskirts.
- They are the only gun-armed enemies in entire series.