More like a pride of lions bringing down an elephant, or maybe wolves on a bison.

1v1 dragon slaying would still be more like a badger taking on a tiger.

Player characters (as opposed to non d&d dragon slaying stories) aren't usually as ill prepared as a cat is vs a human, and rarely "hunt" alone. PCs have better weapons than claws and teeth, and the ability to coordinate attacks reduces the advantage of size and power the dragon has more than the comparison between a cat and a standard, unarmed human.

I do, however, love the idea presented :)

Source? A Commoner has 1d8 hp compared to a cat's 1d4. A cat's AC is 2 higher, but a Commoner's attack modifier is 2 higher. If the Commoner has a club, they're dealing 1d8 damage instead of 1d4, but even without that it's the same damage. A cat can absolutely win if it gets lucky. After all, one in eight commoners have only one hitpoint, but reliably?

Also, I don't think the fight's really comparable, since at low levels randomness matters a lot more. A Commoner is equally likely to have 1 hitpoint as 8. An adult red dragon is 95% likely to have HP from 227 to 286. And likewise, when you're dealing damage, it would be a lot more consistent.

That said, while a cat can't reliably kill a commoner, a party of four cats definitely can, and going up against a large number of weak enemies is not good in general. Also, dragons just get a few abilities, and depending on the DM maybe a few spells that aren't that high level. Going up against human spellcasters is not a great idea.

According to all known laws of aviation, there is no way a human should be able to fly.

What about donkeys?