It's a play on a bit of Orwell's Animal Farm. The easily-confused sheep learned to say "four legs good, two legs bad" to help them distinguish between animals and humans.
I havent heard the audio book version but I have to assume they say, "baaad."
My handle (Hey! Handle - i love double- entendres!) could have been ThreeLegsAreEvenBetter, but that seemed a little long. (Hey! Long!)