After way too much of Pooka Curse's
and Rin Pin's
art, I've finally come up with my own Rise of the Guardians AU.
In my version, Jack ran afoul of Pitch Black long before the movie timeline. Pitch's nightmares made a feast of Jack, but curiously enough, at some point they just lost interest, leaving behind Jack who had been reduced into a child, who apparently had no memories of his prior existence. Pitch left the Frost kid to fend for himself, and soon after Little Jack was found by Dark!Bunny. By the looks of it, Bunny doesn't really know what to make of this new looks-human-but-isn't-human.
And yes, that's a piece of his old staff Little Jack's clutching there. He doesn't really know why it's so important, he just instinctively knows that it's a special stick, and if he looses it, he'll never find another one like it.