The Opera ghost really existed. He was not, as was long believed, a
creature of the imagination of the artists, the superstition of the
managers, or a product of the absurd and impressionable brains of the
young ladies of the ballet, their mothers, the box-keepers, the
cloak-room attendants or the concierge. Yes, he existed in flesh and
blood, although he assumed the complete appearance of a real phantom;
that is to say, of a spectral shade.

Auteur: Gaston Leroux