Beerus is Mr Kat's alter-ego.
But you still suggested that Kat is "HIMSELF". That is true, but you might need a closer look at the clues and the mysteries of this similarity.
In the episode, "Menace the Dennis",
Kat turns plain water into milk, but Dennis (Coop's friend/sidekick) stops him by dropping the hot sauce into the milk, causing it to bubble and steam. But as Kat accidentally falls into the steaming milk, it dawned upon us that this was similar to how "the Joker" came to be. But could it be enough to do the same???
The thing we failed to realize is that the place where Kat is, is an industrial park. And Kat had tried to make partial toxic fluids into dairy products. But the striking part as Kat falls at the last part, is that he could've breathed in the chemicals through his nose as he swam in the toxic waist, incredibly survives without the chemicals melting the skin off his flesh .
During all the episodes in every season, he becomes more hot-headed, more moody against others and everything that interacts with him. That is because in a cats way of knowing, he is actually in pain, in some sort of transformation process. If you know about how "the Incredible Hulk" is in local media, is that he is always angry, attacking every villain he encounters.
But then at the final episode, he said the first words he had ever spoken in the Kid Vs. Kat series,
Those were the last words coming from Kat, before Kid Vs. Kat had canceled for what felt like years.
After a month or two,
"Dragon Ball Z: Battle of Gods" came out in 2015.
But one of its villains, the God of Destruction Lord Beerus, had the same characteristics as Mr. Kat, but with clothing. Kat never has clothing but a collar.
...Could it be possible?? of course not, he wouldn't be Mr. Kat from that cartoon TV show we used to watch, no way could the kid's arch villain mutate into a homicidal brute such as the Destroyer himself, right???
Those questions remained unanswered, but the one thing in our minds however, is that if Mr. Kat is Beerus, then how did Beerus call himself.. "GOD OF DESTRUCTION"?
SIMPLE! - The injuries to Kat's head as he smashed into objects must of caused him to loose memory, for instance,
in the last episode, "The Kat went Back",
Kat falls off the rocket and lands "face first" into the floor below. That landing must of done the trick! Before interns and the show's creator, Rob Boutilier, got involved and messed it up.
Kat would've remembered Millie's name and his memory would've come rushing back to him, but alas, his mind remains hollow, black as pitch.
He had grown super-powers also, I know what you're thinking, "does Kat already have powers since he's an alien?" Yes- but that's not the entire case.
You see, its because of the radiation. Like how a single seed grows into a tree.
The people still post pictures of Mr. Kat as Beerus, and others state that Kat and Beerus is not on the same cloth.
But if you still think that is not possible for Kat being the God of Destruction himself, then look closer, dive into the mystery and see for yourself, that anything can pull FACT, away from FICTION.