Someone snuck in the newborn puppies.
Cats and dogs don't mate, and if they did, their DNA wouldn't let anything fertilize. The biology is just too specific. Two very different species can't breed.
It's like saying a man could fertilize fish eggs. It can't happen.
There was a Nova the other night that was remarkably interesting, about a family in Turkey that walks on all fours.
Alot of it delved into genetics, and it talked about how scientists are still stunned that most of our genes are shared with most other critters.
For instance there is a gene called FOXp2 that enables humans to have speech.
Thing is, dogs have it. Birds have it. But the version in humans underwent two major mods in the last 200,000 years or so. (Don't ask me how they know that)
If we took the human version and spliced it into a dog???
But nonetheless, I agree with you. My position wouldn't be that it was impossible, but that it is vanishingly rare.