According to Jewish law (Halacha), one is Jewish if his or her mother is so. It doesn't matter if the father is Jewish, half-Jewish, Swiss, half-Swiss, or even alien. As long as the mother is a Jew, that's all that matters.
But what if someone doesn't have a mother? Impossible, you say? Well, in the real world, obviously so (until the Earth is taken over by an army of robots, but why would we ever discuss that), but in fiction, that possibility is open. So we present you Frankenstein, or, more specifically, Frankenstein's Monster. Motherless. But Jewish?
For if there is no mother, we have to look at the father, and for surely, Dr. Frankenstein (DOCTOR! FrankenSTEIN!) must have been a Jew, which would make the fabled monster one of our own!
Alas. As we've discovered before, a last name is not enough proof, even for fictional characters. For there is nothing to suggest, other than that name, that Dr. Victor Frankenstein, son of Alphonse Frankenstein and Caroline Beaufort Frankenstein, was Jewish. In fact, he was Swiss. Which would make the Monster Swiss as well. And that's perfectly fine with us.
Seriously, who needs Frankenstein's Monster, when we already have The Golem?