Caliban is, most famously, a monstrous character in William Shakespeare's play The Tempest. However, the reference to the mirror is from another work: Oscar Wilde's preface to The Picture of Dorian Gray. In it, Wilde says that "The nineteenth century dislike of Realism is that of Caliban seeing his own face in the glass. The nineteenth century dislike of Romanticism is that of Caliban not seeing his own face in the glass."  As Mulligan pulls the mirror away from Daedalus' face, he says "If only Wilde could see you now," as if to suggest that Daedalus has somehow opposed Wilde's aphorism.