The Nightmare Before Christmas
Halloween Town is filled with ghosts, goblins, witches, mad scientists, and the Pumpkin King himself, Jack Skellington. Jack lives to trick and treat, but is getting to a point where he's looking for more than just the next ghoulish scare.
One day while walking through the forest he stumbles upon a tree-shaped door and into Christmas Town, a place so unlike his home that he is immediately taken by its bright colors and twinkling lights. Instead of screams of terror there are screams of delight and everyone is in a festive spirit of giving. Returning back to Halloween Town with the knowledge of this new place, Jack persuades the horror denizens to take over Christmas and he, himself, will become the new Santa Claus.