According to the Wikipedia article, the house that the movie was filmed was one of the houses that belonged to Francisco Franco and Naschy spent his free time exploring and rummaging throughout the house.
A cover of the album "Too-Rye-Ay" from "Dexys Midnight Runners" can be seen in one of the scenes.
A cover of the album "Raise!" from "Earth, Wind & Fire" can be seen in one of the scenes.
Geneviève can be seen reading a book by Marry L. called "Fischer".