The story is called Kis Gömböc; the term itself refers to one of the many foods you get out of a pig slaughter. It is, essentially, all kinds of odds and ends stuffed inside the pig's bladder. Kinda like haggis, except more icky.
Story goes that a family slaughtered a pig (that always happens in the winter), used up all parts of it, and towards the end of winter, only the kis gömböc remained. It hung in the attic in the cool and dark, and one day the mother sent her youngest daughter up to fetch it so they could eat.
And instead, the gömböc ate the daughter.
Second daughter gets sent up; never returns. Third daughter follows; doesn't come down. Same thing happens to mother and father, and by this time the gömböc is so large it falls down, rolls down the stairs and out of the house, and starts devouring people. Eventually, after quite a few casualties, it happens to eat up a swineherd who just happened to have a knife, and he cuts the gömböc open from the inside, and lets everybody out.
Now, this is a story that exists in a few variations; in some of them, the culprit is a doll of some sort (it is generally seen as a silly children's story). But I think a dead pig's bladder filled with bodies rolling down the street is pretty much the stuff of nightmares.
In Hungary, the pig slaughter slaughters you.