Unlucky Yarn

You get a black cat in a pointed hat that trots along behind you. Fall too far ahead of it, or jump, and it produces a broom and flies after you, which is the whole gag. It is one of the better looking pets for the effort of animating it, and the hat is lifted straight off a certain wizard in the caves.

This only exists inside Goodie Bags, which only exist during the Halloween window, and the roll inside the bag is thin. Once you multiply the bag drop by the yarn roll, it is close to the rarest thing an ordinary enemy can hand you, in the same territory as the Bat Hook. Plan on a full Halloween of farming rather than a lucky evening, and open bags rather than hoarding them.

The seasonal mirror of this is the Dog Whistle out of Presents. Same idea, opposite holiday, and neither one is remotely easy.