"Let's go a-huntin', said Risky Rob, Let's go a-huntin', said Robin to Bob, Let's go a-huntin', said Dan'l to Jo, Let's go a-huntin', said Billy Barlow." They hunt a (rat/possum), kill it, cook it, and divide it. All get sick except Billy, who feels fine.
Thought by many to be an Americanized version of "The Cutty Wren." The similarity, both in form and in subject matter, is there -- but the two have gone in such separate directions that it seems better to keep them distinct; it is barely possible they are independent (and quite possible that "Billy Barlow" is a deliberate parody).
I can't help but add Paul Stamler's comment, though: "If this is independent from 'Cutty Wren,' I'll eat that possum." (Yes, but would you eat the rat?) - RBW