To understand how cats could have taken over New America and subsequently committed interplanetary genocide, one must first grasp how an Evo-Virobac Sterilizer Grande functions.
Earth borne viruses and infections had been nearly eradicated by the 23rd century, or at least relegated to the lower levels. Despite fantastic advances in everything from targeted advertising to recyclable food bricks, this was a dark time in the humanitarian history of Earth.
Society was divided between the upper classes and the lower. The wealthy and unforgivably lucky upper classes enjoyed sunlight and all of the amenities that could be crammed into their vast network of gorgeous sky cities, while the lower classes endured a damp grim life filled with hard work, mold, and the very real probability of being shat on by their betters in the heavens.
Because the groundwater that lay in abundant fetid pools on the lower level was teeming with live filth, and because filtration systems were costly and usually only produced one ounce of cleanish water per every pound of gunk removed, the poors mostly relied on rainwater for cooking, cleaning, and drinking.
Unfortunately their view of the sky was severely limited due to the glorious sky cities, and so it was very difficult to tell whether or not it was cloudy. The Poors of this sad and gross world had a saying, "Don't trust the rain and watch out for turds".
Of course the frequent raw sewage rain was a problem for the lower level, but their biggest problem was disease. A paper cut was a death sentence for a Poor. The infant mortality rate was through the roof and long defunct diseases had made an impressive comeback in this muggy and bacteria nurturing environment.
The 23rd century also heralded the first visit to Earth by the Fralzbs. This race of gentle genius arthropods from the Walmart Galaxy did not arrive empty handed. the Fralzbs carried with them a method for unlimited clean energy that utilized a dimension bleeder so simple and tiny that it could be handled by a child, space-bend travel technology, and a virulent disease that wiped out all of New Dallas.
The sky city people weren't used to becoming ill and they certainly weren't used to dying in ugly or dirty ways. These guilded bastards had their own saying, "If the universe wanted me to get shat on, gang-raped, and murdered before my tenth birthday, it would have made me a Poor".
The Fralzbs's disease wasn't given a name because unlike the lower level where disease was rampant and it was useful to know how many and what you had, this Fralzb thing was the only sickness going around up there.
If you were sick, you had "It" and if your family didn't kick your flaming corpse loose to bump and thud its way down the scaffolding to the dark world below a.s.a.p., they would also get "It" and be dead soon enough.
When this disease hit and bodies started dropping, Earth's top sky city scientists got to work immediately along with the guilt ridden Fralzbs to find a remedy.
That is why the Evo-Virobac Sterilizer Grande was invented.
And now for the how.
The initial Taj Majal sized device and subsequent much smaller versions function by identifying and altering a creature's stem cells.
In a normal Earth body, the stem cells are masters from which all other cells are copied. The Evo-Virobac Sterilizer Grande causes the stem cells to bond with whatever diseased cells are present. In this way, the creature's cells infects the germs rather than vice versa.
After the initial bonding, these new cells are forced through a few billion growth cycles. Technically, an entirely new species is "born" with each new growth cycle. This would be a problem were it not for the evolution binder, which is a clump of original stem cells that are kept pristine so that they might do battle with the new cells for the rest of the creatures' life. This creates a stalemate, or evolutionary stall. In a very real way, the treatment works by tricking the disease into believing it has won.
When word got out that a cure for all disease was making life on the upper level even more mind-blowingly wonderful than it had been before, the Poors began to get restless. They had been dying at even more phenomenal rates now that "it" had made its way to them through the hygienically inspired dumping of flaming diseased corpses from above.
A cautionary council of 99 upper level kings and one representative from the Poors were called together to discuss whether to lend the lower level losers some of these new miracle cure machines.
The Poors representative, famed autodidact and president of old New York Jim Reefer, was of course in favor of sending down a few dozen of these infinite energy utilizing machines to aid his misery addled fellow petri dishes.
The primary argument against sending machines down was that the Poors hadn't contributed to the development of the remedy. A secondary and more sinister point was that it would be useful to have a live breeding catalog of every disease humanity had hosted for scientific and military purposes.
Jim Reefer spoke up valiantly for the Poors. In less time than it took for a Sky City turd to fall onto a Poor's head, upper level housewives and romantic university students began to fall in love with this eloquent and handsome man.
Reefer knew how to work a crowd. His passionate speeches often ended in wracking coughs as he sprayed bloody spittle against the inside of the plastic bubble he was forced to wear to council meetings.
Reefer reminded the upper kings that while the Poors hadn't done anything to help with the cure, they were certainly dying at record rates from a disease that had been literally dropped onto them by the upper level.
The most popular of Jim Reefer's arguments, and perhaps the most revolutionary, was the simple question he posed of "Why not?". Why not help? Why not cure all disease everywhere? Why not share the good? Why the hell not?
"Why not?" shirts and hats began appearing on campuses and the phrase spread into music videos, targeted advertising, and fast food brick commercials.
After months of heated debate and a few million deaths, 52 of the 99 upper level kings relented and the "Why Not?" initiative passed. This began the months long process of deciding where, when, and how to send a dozen Evo-Virobac Sterilizer Grande's to the lower tier.
Unfortunately, Jim Reefer succumbed to a brutal combination of syphilis, shingles, the flu, tuberculosis, and an infected hangnail just two days later.
The Evo-Virobac Stabilizer Grande's all had built in dimension bleeders so they could be used around the clock, and initially, they were. It wasn't long before one of these impossibly huge and complicated machines began to fail in a most spectacular way. However to be fair, when dealing with alterations of biology, any failure is going to be spectacular.
Machine 12 was installed in old Houston, an area hit particularly hard by the giant space bug's disease. The aspect and timing of machine 12's malfunction was a perfect storm.
Evo-Virobac Sterilizer Grandes were designed to run themselves. The diseased simply stepped in and pressed the button, and stepped out when done. One at a time, idiot proof.
The first few months required around the clock guards to keep gasping and oozing dying people from rushing the machines, however, after the majority of the population were either healed or dead, these behemoths of alien technology mostly just sat around collecting dust.
Nobody was in or around machine 12 when a healthy and bright eyed small boy with turd dust in his dark hair approached with his glassy eyed cat, Janet.
For several months, Janet had been dying of feline leukemia. These machines could heal any creature, provided it had stem cells. It was common for Poors and Sly City dwellers alike to bring pets for treatment once the hellish initial rush to heal humanity had faded. What was unfortunate about this particular day, was that machine 12's evolution binder was malfunctioning.
Without the evolution binder to maintain the evolutionary stalemate between old cells and new, any creature in an Evo-Virobac Sterilizer Grande would evolve rapidly. The end result of this was that in just a few short moments, any creature placed into machine 12 could skip a few billion years of evolutionary advancement. That is exactly what happened when Janet was placed inside of the machine.
History from that point on is a little sketchy. Who can say whether the shit-dusted boy who cared enough for Janet to use machine 12 to save her was rewarded for his kindness with a speedy death?
It's anyone's guess how quickly after gaining a significant boost in cunning, intellect, and strength, Lord Janet hatched her plan. We can only marvel at the machinations of this brand new creature, forced into artificial evolution to emerge reborn.
In just four years, Lord Janet had used machine 12 to hyper-evolve billions of cats. Within ten more years, Lord Janet and her army of vicious yet disarmingly soft brutes had bested both the lower and upper levels and had enslaved the gentle Fralzbs's in order to use their ships to conquer the burgeoning moon colonies.
There were two options under Lord Janet's rule, slavery or death.