Mouse Transformation is a new feature introduced on April 30, 2011, on version 0.154.
Mouse Transformation is currently enabled in maps 200-210. These maps appear only if there are at least 10 mice in the room.
In these maps, mice can transform into objects in order to cooperate and get the cheese. These objects are:
Mouse Transformation icons appear in the shaman items box on the bottom right of the screen. Once a mouse is transformed in an object, it can revert to its original form by clicking the mouse icon.
According to game co-creator and administrator Melibellule, the concept of mice "transforming" into objects (thus the name, Transformice) was to be the system of moving about on the map, but proved to be difficult or impossible with only a few players in a room. As more have begun to play the game, the concept has been re-introduced into a few maps.