Swat Kats/WMG

There are no countries as we know them in the Swat Kats universe.
There are only independent city-states, of which Megakat city is one of the more prominent. This explains why Megakat city seems to be one huge, self-sustained industrial and political entity with its own private military-police force embodied in the Enforcers.
 * That would explain why Manx is so eager to attract foreign business and never seems to have to answer to anyone higher than himself.

There were once humans, but...
In the final days of humanity, human DNA was being combined with kitty cats to create a race that could pick up where humans left off. Of course, humans would be prehistoric to the kats. And ironically, most of the villains are distant descendants of Ted Turner.
 * Actually, they're on another planet entirely. The original plan for "When Strikes Mutilor" had.

Dark Kat killed Feral's wife, or someone very close to him.
That's why he was so insistent that he be the one to take him down.
 * He used her as a human sacrifice to gain powers from an evil god or demon.

The series is the ultimate end result of the Ace Combat universe.
Think about it: the Turbo Kat easily rivals - if not surpasses - many of AC's superplanes such as the Wyvern and possibly even Falken. T-Bone and Razor might have gotten the idea from archeological digs that brought up centuries-old fighters, one of which was fittingly the F-14 Tomcat. How do they find out about this stuff? Their version of the internet, of course. How the Kats come to replace Humans on Strangereal is anyone's guess, though. Perhaps some of the Monsters-of-the-week can actually be traced back to "ancient" weapons from AC's world. This also means that there could be a city-state (as per an above WMG) trying to build and perfect an airborne fortress akin to Gleipnir, or an uberfighter that rivals the Fenrir (or rather is Fenrir).


 * I guess Belka finally gets its revenge in this WMG. They wipe out the world and start anew... only with kats instead of humans.

T-Bone remained partially mutated after "Mutation City"
Even though most of the physical signs of his being a mutated frog-kat vanished, the anti-mutagens couldn't restore him entirely to normal. That's how T-Bone managed to swim at the end of the episode when he sank like a rock every other time in the water: he's still partially a frog. It's also how he managed to get to Razor so fast: heightened senses and increased speed and stamina.

Someone will finally buy the rights and make more episodes!
And they'll hire Samuel L. Jackson to be the voice of Commander Feral. It shall be AWESOME.
 * I just pictured that. Imagine Feral staring at the Monster of the Week and saying, under his breath that "We need Chopper backup." Goosebumps, I say, goosebumps.

At least one of the bacteria monsters divided offscreen.
A Fridge Horror explanation for the blooper regarding the inconsistent amount of eyes on the monsters in "The Giant Bacteria" is that the third, two-eyed monster divided at some point, leaving a fourth (final) monster out there somewhere.

Nobody works in Megakat City's government except Callie and Manx. And it's because of the Megakat Tower.
Manx sinking a billion dollars into his stupid tower (the one in "Destructive Nature") has taken its toll on Megakat City's economy early in the first season, and it seems Manx's answer is massive layoffs and firings. This is most evident by all the menial jobs he gives Callie that a real deputy mayor wouldn't really ever do. This is most evident in "The Pastmaster Always Rings Twice," where Callie is at the museum preparing a press release for Manx about an upcoming exhibit.

Now, of course, this is just a narrative device to let Callie be present when the Pastmaster shows up so she can call our boys. But realistically speaking... why is she there in-story? I'm pretty sure if Manx wanted a press release from a museum for whatever reason, he'd have media staff for that.

The answer: Manx has no media people because he fired them. In fact, City Hall's entire press and public relations divisions have been laid off. It's just Manx and Callie in that big, empty building. Everybody else got fired to pay for the Megakat Tower's billion dollar construction, leaving Callie to juggle God knows how many different jobs at once in addition to being deputy mayor, explaining her crankiness towards Feral, who she already disliked anyway.
 * No matter how good you are, there is no freaking way a single competent person can run a government by herself. A single, relatively small school is already a bureaucratic nightmare in itself. A government for an entire mega-city would need to have an even more complex bureaucracy to run the place. The only way this theory could possibly work is if there is extremely intensive automation actually running the city, with a mayor and deputy-mayor only needed to keep the ultimate decision in the hands of non-machines.
 * I wasn't serious. I'm well aware that it takes a lot of people to run a city, and that the real reason the only people we see are Callie and Manx is because the animators couldn't be bothered drawing extraneous background civil servants. But I just thought the above Wild Mass Guess was an amusing idea. It was only a joke, and I never anticipated someone would actually take it at face value. However, having given it some thought, I'd like to revise my original theory and suggest that while more than just two people run Megakat City, the government is still understaffed. I need only reiterate that Callie is depicted performing a lot of menial tasks you wouldn't normally find a deputy mayor doing. This, to me, implies a lack of underlings and gofers due to a shortage of staff (but not an outright lack of it like I originally suggested), forcing Callie to tackle multiple jobs for Manx..

Steel's surname really is spelled with two E's, and "Steele" on his nameplate is a misprint.
Kind of like Sheriff Dollard's badge saying "Dullard" in To Wong Foo Thanks for Everything Julie Newmar. Steel(e) insisting on his correct name spelling in "The Wrath of Dark Kat" could be a nod to the fact everyone spells his name wrong with an "E" at the end, even on his nameplate. This would mean the spelling in "Enter the Madkat" isn't an error by the writers/animators but a joke about how the other characters can't spell Steel's name correctly.

The show will get a Reboot. Or, a Spiritual Successor.
A lot of good shows are coming back. I wouldn't be surprised if this did. Also, if it turns out to be a Spiritual Successor. Then, it should be that the Swat Kats have evolved to a defense team. Besides T-Bone and Razor.
 * Or it could be a Sequel Series where the Swat Kats have taken over the Enforcers after Feral has left (or got kicked out). Felina is the new commander with T-Bone and Razor in charge of a squadron that handles the same stuff they did back in the day, but with better equipment and a full array of support vehicles all done in the Turbo Kat's colors, of course. Merchandise-Driven isn't necessarily a bad thing.
 * Okay, this is just BEGGING to be made into a fan fic. Especcially since all this could actually work in-universe if Callie were to become Mayor (not to hard a stretch, considering she's already the mayor in everything but name).