Pantz, you are the win! It was the Ragtime Mouse!

Wow, I did NOT expect that to last as long as it did. Anyway, here's the explanation.

"What the hell did you call me?
Look at me, do I look like vermin to you?"
As I've stated before, these lines go together. The Ragtime Mouse is not a mouse, and looks nothing like a mouse. His/Its name was actually supposed to be Ragtime Mouth, which is much more fitting for his appearance. So he's wondering why on earth the player (as I said, it's the player calling him vermin, not any character in the game) is calling him a Ragtime Mouse when he clearly looks nothing like a mouse.

"You're gonna have to work to earn my protection now.
Nothing in life is free, after all."
If you answer all of his questions correctly, he drops a Protect Ring. This is sort of continuing the "story" of the riddle too, with the Ragtime Mouse/Mouth essentially saying he was just going to give you the ring, but then you insulted him by calling him a mouse so now you have to earn it.

"How about we play a little game first?"
Refers to the questions you have to answer.

Congratulations!