Exposure to mutagen ooze transformed brown squirrels into mutant monstrosities. They reproduce inside a human host by hopping into the mouth—but when some hop inside of Raphael, his DNA mixes with theirs to create a new form.

Now the 9' Squirrelanoids have red skeletal bodies with glowing green eyes and mouths. They have secondary mouths in their jaws and their glowing brains can be seen on the tops of their heads.