It's interesting that Oscar Wilde refers to Caliban in the preface of his novel The Picture of Dorian Gray. Wild states that  "The nineteenth century dislike of Realism is the rage of Caliban, seeing his own face in a glass. The nineteenth century dislike of Romanticism is the Rage of Caliban, not seeing his own face in a glass."

Caliban in The Tempest is an original inhabitant of the island and is the bastard son of a witch, Sycorax. He is a base and simple slave who mirrors and contrasts several of the other characters in the plot of play. He is described by Prospero such as a horrible and deformed character, "not honour'd with a human shape“ (Prospero, I.2.283). In some traditions he is depicted as a wild man, or a deformed man, or a beast man, or sometimes a mix of fish and man.

Oscar Wilde uses this character to explain to the reader the nineteenth century dislike of realism. Caliban can see himself in the mirror, and the mirror reflects his terrible ugliness. As a consequence he becomes angry for this reason. In a similar way people don't like realism in literature, because as a mirror the text returns all the negative aspects of life.

On the other hand Wilde still uses this character to explain to the reader the dislike of Romanticism. In this case Caliban can't see himself in the mirror.  He refuses to acknowledge he's own ugliness. Romantic poets and writers stressed the examination of inner feelings, emotions, and use of imagination. They also pointed out the mysterious, strange, and fantastic aspects of the human experience, refusing the reality and the negative aspects of life.