What is the name of this classical piece?

Question

What is the name of the classical piece used when skeletons are dancing?

Answer 1

It's very hard to answer your question because you don't put it in a specific context like a movie or something like that, but Camille Saint-Saens did compose a work intended to depict this exact event: Danse Macabre.

You can listen to it here:
http://www.cscapitale.qc.ca/oree-des-bois/projets/rescol/grandscompositeurs/Saint-Saens/saint-saens.html

Is that what you're looking for?