Gerbillius Doctorus

Gerbillus Doctorus is Dr. Muto's first morph, and it allows him to transform into a mouse. By collecting the 15 isotopes required at the beginning of the game, Muto unlocks this morph. By obtaining 30 DNA from charks, the second stage of the morph, the Rat, is unlocked.

Appearance
When in Gerbillus Doctorus form, Dr. Muto takes the appearance of a white mouse, bringing to mind the white color of "lab rats" often depicted in experiments.

Muto retains his lab coat, "coke-bottle" glasses, streaked hair, and mustache in this form, with a bucktooth growing underneath his mustache. Muto's voice in this form is higher pitched. When attacking with the tail whip, Muto will often let out a high-pitched "Hyah!"

Usage
Gerbillus Doctorus is Dr. Muto's means of traveling through small passages, such as holes in the walls or air vents. It gives Muto advanced maneuverability, allowing him to dodge projectiles and jump on platforms more easily.

Gerbillus Doctorus's method of attack is similar to the Splizz Gun; he can whip enemies with his tail, as well as swallow them whole, reminiscent of the Splizz Gun's Attack and Capture. However, the attack button can be held to charge the whip attack, giving the attack further range. The charge attack can even be held while moving, allowing deadly attacks at fast speeds.

The disadvantage of Dr. Muto's mouse morph is his small size; while it's useful to scurry through cracks in the wall, it puts Muto at a disadvantage in large areas. Muto cannot swim while in the mouse form, and will quickly drown if he doesn't morph back. It's also very easy for Muto to get crushed by props, machinery, and enemies present in game world.