Zero

Zero is a character of Disney's 1993 stop-motion film The Nightmare Before Christmas.

Designs
Zero is a ghostly dog that appears to be made of a white sheet, much like a stereotypical ghost. Like Pluto, he has basset hound-esque floppy ears. His "eyes" are just empty holes in the sheet. Zero's snout is very long and thin, and his upper jaw curls upward at the tip. His nose is a small jack-o-lantern, and his collar is a faded brown color.

Role in The Nightmare Before Christmas
Zero first appeared in the 1993 movie The Nightmare Before Christmas. In the movie, Jack finds the door to Christmas Town while he is taking Zero for a walk. Later, when Jack wants to take off through the thick fog to deliver presents, Zero has to light the way. At the end of the movie, Jack and Sally kiss each other as Zero looks at them. He then flies into the air and transforms into a star.

The Nightmare Before Christmas: Oogie's Revenge
Zero can be called upon by Jack when the enemy is hard to defeat. Zero's only known powers are growling and biting.

Kingdom Hearts
Zero had a relatively small role in Kingdom Hearts, appearing only as a ghostly hallucination.

Kingdom Hearts 358/2 Days
When Roxas finds Jack and Zero in the Graveyard, he is amused to see that the ghostly dog can sense the Heartless's presence around him with his nose. Showing Jack a Carrier Ghost that was hiding in one, Zero is rewarded by a happy Jack while Roxas looks on. Roxas realizes that if he gives Zero a bone, the dog would reveal the Heartless' hiding places. Zero gladly complies, and Roxas completes his missions with ease.

Kingdom Hearts II
Sora encounters Zero again, aimlessly floating around Dr. Finkelstein's lab. When spoken to, he happily barks at Sora and his friends.

Disney Parks
Zero appears in the Haunted Mansion Holiday attraction in the Endless Hallway and the Graveyard scenes with Jack. He also appears in Disneyland's Halloween Screams fireworks show, floating over the castle in a similar fashion to Tinkerbell.

Trivia

 * Zero's "Corpse Bride" counterpart is Victor's skeleton dog: Scraps.