The Trick or Treat Sack is the large sack used by Lock, Shock, and Barrel to kidnap and transport Santa Claus from Christmas Town to Halloween Town. It is made of black leather, and is covered in grinning, orange, jack o'lanterns. It seems to increase or decrease in size depending on what is contained within it.
In the film, the sack is first seen in the Treehouse, during the song Kidnap The Sandy Claws. It is the last item thrown into the trio's walking bathtub before they head into the woods. When it transports the Easter Bunny to the town hall, it has seemingly grown larger. When Lock, Shock, and Barrel return again with Santa, the sack seems to have doubled in size again, larger in diameter than the trio's walking bathtub. It is unknown how the sack's size changes so drastically. When Santa meets Jack for the first time, bits of candy are caught in his beard, suggesting that, when it is not being used to kidnap victims, the group uses the sack while trick or treating.