Problem - 4722
$\textbf{The Pet Inc}$
The Pet Inc is owned by three gentlemen pets: a dog, a cat, and a pig. One day, while they are chatting to each other. Mr. Pig says: "Isn't it a bit odd that our surnames match our species, but none of our surnames matches our own species?" The dog replies: "Yes, but does it matter?" Can you relate their surnames and species?
$\textbf{Answer}$
Mr Cat is a dog, Mr Pig is a cat, and Mr Dog is a pig.
$\textbf{Analysis}$
The dog cannot be Mr. Pig, nor Mr Dog, so he must be Mr Cat. Then it will be clear that Mr Dog must be a pig, and Mr Pig must be a cat.