The famous quote "The next morning, I felt very weak, as if I had lost my virginity" is a mistranslation of the English subtitles in the home video version. What Eva is actually saying in Spanish is, "The next morning, I felt as weak as if I had lost my vitality."
When Dracula first enters Lucy's bedroom in the guise of a bat the long shot shows her looking away from the window towards the viewer. The next shot from the window shows her looking towards the window.
The three brides of Dracula that are seen in the catacombs are not the three that set upon Renfield. The catacombs shot was stock footage from Dracula, and thus the three actresses playing the brides are different.
The first images of the carriage pulling into the town are stock footage from _Dracula (1931)_ and contain long shots of Michael Visaroff as the innkeeper. This gives the proprietor a temporary bald spot which completely disappears in all further shots.
Like Bela Lugosi in the English version of Dracula, Carlos Villarías wore a hair-piece that gave him a pronounced widow's peak. But unlike Lugosi, the toupee didn't rest well and is rather obvious in some shots.