Baron Frankenstein (Frederick Kerr)
The Baron is pompous, self-satisfied, and, supposedly, adorable. He struts about and tells people to go hither and thither and gives the servants champagne to celebrate his son's wedding because the good wine is "wasted on 'em."
He's sure of himself and his position and of his power, and you can sort of see why Henry has decided to go off to create monsters. Better to stitch dead people together and hang out with Fritz than to spend your life with this pompous, boring, snobbish oaf.
Ludwig, Maria's Father (Michael Mark)
Ludwig is the salt of the earth peasant whose grief justifies the rampage against the monster. You'd think part of his anger, and everyone else's, would be directed against Henry, who's the idiot who created the monster in the first place, and then compounded the error by letting said monster get away. But maybe Ludwig doesn't know it's all Henry's fault. It's the sort of thing the nobles don't tell the peasants.
Maria (Marilyn Harris)
Sunny lil' Maria is the adorable girl that the monster tosses in the lake. She's innocent and tragic, and teaches children the important lesson that you shouldn't play with monsters made out of reanimated corpse parts.
Victor Moritz (John Boles)
Victor is the handy backup protagonist. Henry Frankenstein tells him:
"You stay here and look after Elizabeth. I'll leave her in your care, whatever happens."
Then Henry runs off to fight the monster and gets killed.
Or at least, he got killed in an early version of the film. Audiences didn't like that, so the filmmakers changed the ending. Suddenly, there's no need for a back-up protagonist anymore; Victor doesn't have to take care of Elizabeth, because Henry's still around. As a result, Victor's role seems completely pointless. Why is he there? Who needs him? Poor Victor; he spends the whole film looking vaguely noble and superfluous.
Herr Vogel, the Burgomaster (Lionel Belmore)
Herr Vogel sucks up to the Baron and tells the peasants what to do. He's middle management, in other words. Kind of like Fritz (see Characters: Fritz).