Alternate Reality Mr. Kat is an alternate reality incarnation of Mr. Kat. Unlike his original counterpart, this alternate future version of Mr. Kat managed to succeed in conquering the Earth thanks to Coop Burtonburger altering the timeline as such Millie Burtonburger never found him. He is far worse than the original Mr. Kat, as he enslaved the entire human race and apparently transformed Bootsville in the Earth's capital city after the Catnipians abandoned Catnip.
This tyrannical version of Mr. Kat was born after Coop Burtonburger changed the timeline to have his original and peaceful life back again. As such, in order to do that, he needed to avoid his sister Millie from knowing Mr. Kat at the woods of his house at Bootsville.
In the episode "Kat to the Future, Part I", after Coop discovers that there were two Mr. Kats instead of such one, he uses Kat's newly created time machine to go back to the past and fix himself from commiting an error at a soccer game which took place early that day. As such, Coop goes back to the past and warns his past self to avoid commiting that error, leading the past Coop to win the soccer game. Then, they later use the time machine to bully Mr. Kat and his double. Though Dennis warns them to not use the time machine because it could produce some changes or paradoxes, the original Coop decides to go back the day Millie found Mr. Kat and brought him to home. Said and done, Coop returns and avoids his past self to went for his baseball ball and departs for the now supposedly better future.
Unfortunately, once Coop returned to the future, he finds his house's basement such a mess, and hears some meows in the first floor. Terrified on how many cats could Millie have for not discovering Mr. Kat, Coops opens the door and finds something horrible: Mr. Kat is relaxing at a mattres, he has two giant Catnipian bodyguards & Lorn and Harley in addition to his present self are his slaves, though his present self is Mr. Kat's most favored slave in comparison to Lorn and Harley, though he tends to abuse him sometimes like using his scepter to inmobilize him. In fact, when Coop avoided Mr. Kat to be discovered and brought to his house by Millie, he allowed him to perform his task without setbacks, thus conquering the Earth and enslaving the human race apparently once the Kat Kommander either died or retired.
In the next episode "Kat to the Future, Part II", Coop is discovered by the enslaved Lorn and Harley, who upon discovering him, report to the Catnipian bodyguards that Coop is without a training collar, leading the bodyguards to chase Coop to send him to the Correctionary Cat Ball, though he manages to escape, only to find that his house is Kat's Headquarters, Bootsville is now destroyed and all his friends, teachers or Bootsvillians are now enslaved by the Catnipians, who now live at their houses. A patrol of Catnipians attempt then to catch Coop with their mechanical dogs, but he too escapes from them and seeks hospice at his father Burt's business the House Of Swap, where he finds Burt, Dennis, Phoebe, Old Lady Munson and Millie as members of the Resistance. Though they initially think that Coop was send by the Alternate Reality Mr. Kat to reveal their location, when Coop reveals that he has a time machine, they help him to infiltrate into Kat's Headquarters. After the Alternate Reality Mr. Kat concludes from his throne rooftop that his Catnipian army is being defeated by the Resistance, he decides to take the matter on his own paws, attempting to take out Coop with a bazooka, but Coop managed to use a wool rope to lead Kat to blown up the platform where he was standing, falling above Millie.
Once Millie was ready to presumably finish off with the Alternate Reality Mr. Kat, Kat uses his appearance to convince Millie to spare his life, nearly succedding, but Coop fights against him to avoid Millie from commiting the same error she did in the original timeline by leading Kat into the kitchen in order to reach the basement. On the other hand, Millie gets outnumbered by Kat's army and is ultimately subdued and caged in a cat cage along the other Resistance members, who are sure that they have lost though Millie and Burt are sure that Coop will repair the past. Meanwhile, the Alternate Reality Mr. Kat attempts to take out Coop with his scepter by faring a deadly laser. Unfortunately, the enslaved Coop appears on scene and though he intially refuses to disobey Kat's orders. From being astonished, Kat decides to kill Coop once and for all after this one concludes that his enslaved self will help Kat, but for his surprise, the enslaved Coop decides to fight the Alternate Reality Mr. Kat and buys time for Coop to return to the past with the time machine. It's completely unknown what happened to both the Alternate Reality Mr. Kat and the enslaved Coop, but given that the enslaved Coop was disarmed, the Alternate Reality Mr. Kat most likely killed or subdued him and send him along the other Resistance members, though there could still be the slim possibility that Coop could have killed his reality's Mr. Kat.
Whatever was the fate of both the Alternate Reality Mr. Kat and the enslaved Coop, once the original Coop returned to the past, he warned his past self and everything, minus the Burtonburger's house, returned back to normal, thus erasing the Alternate Reality Mr. Kat and his tyrannical empire from the future. As by the next episodes the Burtonburger household is without spots, it's likely that Coop fixed this error by traveling with the time machine again or the house was repainted by Burt.
- It's exactly unknown why the Kat Kommander isn't the ruler of the Earth in this alternate reality, given that he was the one who gave Mr. Kat the order to conquer the Earth for the Catnipians in order to use it as another planet for them to live, as revealed in the series finale "The Kat Went Back, Part II". Though there's the possibility that Kat overthrown or killed him due his bully nature, that's very unlikely to have happen in this alternate reality. Since Mr. Kitten was Kat Kommander's son, it would be highly suspectable that he would have been his heir as ruler of the Catnipians once his father retired or died, but it could be possible that Kat Kommander selected Mr. Kat to be his heir as his son was too rebellious and would have been likely a bad ruler. The proof of this is that Kat Kommander's face was sculpted in Mount Rushmore, as had Kat would have killed or overthrown him, he would have most likely not sculpted his face at Mount Rushmore.
- It's also not known why Kat's Girlfriend isn't seen with him in this future, as she also seemed to hate Kat Kommander and she wouldn't have been angry to Mr. Kat in case he overthrown their ruler.