I beheld the wretch—the miserable monster whom I had created. He held up the curtain of the bed; and his eyes, if eyes they may be called, were fixed on me. His jaws opened, and he muttered some inarticulate sounds, while a grin wrinkled his cheeks. He might have spoken, but I did not hear; one hand was stretched out, seemingly to detain me, but I escaped and rushed downstairs. I took refuge in the courtyard belonging to the house which I inhabited, where I remained during the rest of the night, walking up and down in the greatest agitation, listening attentively, catching and fearing each sound as if it were to announce the approach of the demoniacal corpse to which I had so miserably given life. 

Oh! No mortal could support the horror of that countenance. A mummy again endued with animation could not be so hideous as that wretch. I had gazed on him while unfinished; he was ugly then, but when those muscles and joints were rendered capable of motion, it became a thing such as even Dante could not have conceived. 

Basic set up:

The scientist Victor Frankenstein recounts bringing his monster to life in a scientific experiment. And he's horrified by how ugly the dude is.

Literature pro-tip: Most people think that "Frankenstein" refers to the creepy green dude with bolts in his neck. That's wrong: in Mary Shelley's novel Frankenstein is the name of the narrator, the scientist who creates the monster. In the above scene, Frankenstein, the scientist, is getting his first look at his monster, after he has brought him to life. And what he sees makes the hair stand up on his neck.

Frankenstein's monster is one of the earliest examples in sci-fi of a non-human, or semi-human character. He's made up of the collected bits of various corpses. Yuck. Is it any wonder he's ugly?

This monster is one of the most famous characters in English literature, and he's also a great example of sci-fi's emphasis on non- or semi-human characters. He may not be an alien from outer space, but he sure is pretty weird (and disgusting).

Sci-fi often deals with the confrontation between humans and non-humans. In this passage from Mary Shelley's novel, we see that confrontation in action. The scientist Frankenstein has spent years creating the monster Frankenstein (it's a little unfair to call him a monster since he's actually a pretty nice guy in the novel. He's just terribly misunderstood).

But when the scientist confronts his creation, he's horrified. The monster is as different from a "human" as could be. The narrator's horror at his creation is reflected in his very exaggerated language. The narrator describes him as a "demoniacal corpse" and more frightening than a "mummy" brought to life. The narrator is confronting the Other here—something (someone?) completely different from what he is familiar with.