In "Cathedral," the narrator's reaction to Robert's impending visit is decidedly unenthusiastic.
He gives two reasons for not being enthusiastic about Robert's visit. First of all, he doesn't know him. And secondly, he's uncomfortable with his blindness. As the narrator freely confesses, his idea of blindness comes from the movies. There, the blind are routinely portrayed in a negative fashion—as slow-moving, humorless, and dependent on guide-dogs. As the narrator assumes that Robert will be like this, he doesn't welcome his imminent appearance in his home.
Yet Robert surprises the narrator, disabusing him of his prejudices concerning the blind. He does this by drawing a picture of a cathedral with him, an experience that gives the narrator a unique opportunity to step outside of himself and see things from someone else's perspective, thus enabling him to challenge his long-standing prejudices.
As a consequence, the narrator is not just surprised at Robert, who challenges all the assumptions he's had about blind people; he also surprises himself by showing himself capable of entering a new realm of experience.