In the most talked-about scene, Paul Naschy was set upon by real rats. He had to be inoculated against possible rabies. It was also María Elena Arpón, and not a mannequin, lying on a slab with the rodents nestling and nibbling all over her. Some of the rats were burned alive on camera.
Permission was given to use a real corpse for the head-severing scene, but Paul Naschy) took two swigs of whiskey because he couldn't get past the first cut into the throat. A dummy head was used thereafter.