Mutant test-squirrels are enemies in Going Commando encountered in the Megacorp Armory, Todano. They are large and aggressive mutated squirrels, with dark red fur, a yellow belly and yellow stripes on their tail, and a blue tongue. Native to Todano, they were originally used by Megacorp for weapons testing. One such squirrel was named Bobo, who was transported by Megacorp's Z-X9 galaxy cruise rocket into a black hole; he never returned, but was remembered fondly by Megacorp.
Eventually, protests from Squirrel Rights groups forced Megacorp to release them into the wild, where they instead became hostile, feeding on small wild animals and tourists. Ratchet and Clank encountered them in the outside areas around the Megacorp Armory during "Explore the Weapons Facility", in which they attacked the tourists, and the mission "Search the rocket silo".
Mutant test-squirrels are relatively small enemies, but are surprisingly durable and can deal a decent amount of damage if they overwhelm Ratchet. While most are found over the ground, several will drop out of the trees, and during the tour attack tourists that are at the rear from the group. Weapons that do strong damage in an area of effect, such as the Minirocket Tube, Bouncer, and Plasma Coil, are ideal against them. The Sheepinator can also prove useful once acquired for it instantly turns them into a sheep.
Two skill points relate to the mutant test-squirrels: "You're my Hero" is obtained by protecting all tourists from the squirrels. When protecting the tourists, the Plasma Coil, especially if upgraded to the Plasma Storm, is ideal as it will deal damage to several squirrels at once without harming any tourists. "Try to Sleep" is obtained by morphing sixteen of them using the Sheepinator.