In "Chaos in Crystal", after Rex Shard is defeated and made normal again, everything he turned to crystal reverts to its normal state. Consider the warden he turned to crystal... and then shattered. That would've turned into one messy office.
Every single kat skeleton we see (and we see plenty of them) has a skull complete with ears.
Why did Professor Hackle, the brilliant cybernetics scientist, think that two random (dead) strangers would be psyched about being turned into a robotic Maid and a robotic Chauffeur? Sure, he had no way of knowing they were dangerous criminals when they were alive (except that his island home shares the bay with a maximum security prison), but he just assumed they would be leap at the chance to spend their new lives (with new, shiny, super-strong and durable bodies) as household servants.
There's quite a bit of fridge logic at work when it comes to the Metallikats, because his plan to make them his maid and chauffeur came after he knew they were Mac and Molly Mange. He seemed to understand the second time that they couldn't be fixed, at least. And then there's the whole question of leaving your freshly-activated, highly experimental robots in the same room that you keep your experimental weaponry and heavily-armed hovercar. Hackle shows an incredible amount of Genre Blindness.