They were just ordinary rats until The Rat King injected them with a special mutagenic growth serum. This made them horrible disfigured monsters! Although, what the Rat King really wanted was humanoid rat people.
These rats are about 10-15ft long counting their tails. Most of them seem to have hunchbacks with black fur with large wrinkled faces and big, deformed, orange teeth. The rats all have large pointed fingernails and big pink rat tails.
- Caligula - A giant rat who serves as Rat King's mode of transportation. He is named after the historical Roman Emperor Caligula.
- Claudius, Nero, and Commodus - The other three giant rats that are named by Rat King. They are named after Roman Emperors Claudius, Nero, and Commodus.
Even know they are large, heavy rats, their weight won't get in the way while hunting down humans with great speed. These giant rats are able to snap at any of their predators with their giant sharp yellow teeth. Like all rats, these guys are able to squeeze through any whole, no matter the size. They have strength to carry humans. Their endurable and stamina are pretty well then normal rat abilities able to take more pain from the Turtles and Casey attacks.
- They are the second mutants to become larger versions of themselves when mutating. The first ones were the Mutant Wasps.