Eric Grundhauser discusses the obscure and weird case of the "Zaragoza goblin" from 1934 here, for Atlas Obscura.
The Palazón family suffered for months from a strange voice that seemed to emanate from the stove in the family home. The voice, or who- or whatever it represented, seemed to know the answers to questions put to it, which mystified the family, neighbors, and police. The family hired workmen to investigate the source of the voice. Finally, says Mr. Grundhauser, "[T]he local magistrate, who was eager to restore logic and order to the city, deemed the case to simply be an anomaly and the police withdrew. However, things were far from over."
Eventually, the governor of the province decided to end all discussion by announcing that the family maid, Pascuala Alcocer, was behind the strange events. She was, said the official, a victim of "unconsicous ventriloquism." Not everyone was convinced, however.
Here is more discussion of the Zaragoza Goblin (or duende) from Xavier Ortega.