Guinea Pigs?

What are guinea pigs? Or better, why are guinea pigs?

Guinea Pigs, Guinea Pigs

Guinea pigs are some sort of creatures.

I don't really know what they are.

But they seem to lack small piggish features,

though I squint from up close or afar.

Either way, they look not like a guinea,

the fowl kind I mean to say now,

nor the white be-winged horse with its whinny

nor the high-over-the-moon-flying cow.

For me, guinea pigs just don't go whole hog.