Other mistake: When Jack first arrives in Christmas Land he doesn't know what is falling from the sky (snow) but he somehow knows that the children are throwing snowballs.
Other mistake: When Jack is handing out presents and the first house he goes to a kid catches him, and he hands him a present. Well you can see the bag of presents right next to the kid, but he never takes it back up, yet has it again later in the movie.
Answer: Except they're a reanimated corpse and a skeleton. They are either already dead (or undead), or, given how things seem to work, the normal natural laws don't apply to Halloweentown.
Greg Dwyer
But how did Santa survive the Iron Maiden? Especially with how big he is, he certainly would have been killed.
You're trying to apply the rules of the real world to fictional magical beings.
LorgSkyegon