The Mutant Rats first draw attention to themselves after one attacks a homeless man in New York City. H.E.A.T. then began to track them down, and were attacked by a group of Rats before being chased off by Godzilla. They were then hunted by a group of poachers, and teh two groups made their way into the Giant Rats' nest, where they were able to corner the assailants, but they are buried in their burrow by Godzilla and drowned before they can cause the humans harm.
One of the Mutant Rats (the biggest one with the dark skin) has survived and joined to Crustaceous Rex, King Cobra, Gusano Gigante, Giant Mutant Bee, Cryptocledius and Giant Bat controlled by Tachyon Aliens. He disappears after they launch their attack. His final fate is unknown, he is presumed still alive at large or killed in the battle.
Three different rats sizes shown different abilities of their size. Small Rats
- The smaller rats have tried to outrun Zilla Jr. with amazing speed.
- The smaller rats are extraordinary jumpers, being able to jump on top of short buildings.
- The medium-sized rats have the strength also carry humans by using one arm.
- The bigger rats are much stronger then the other two types of mutant rats as one shown to be able to pull entire dumbster that was completely full with no sign of struggle.