How does Sir Andrew feel about Cesario in Shakespeare's Twelfth Night?
One place we learn of Sir Andrew's opinion of Cesario is in Act 3, Scene 1, the first scene in which Sir Andrew meets Cesario. Here, we learn that Sir Andrew is very impressed by Cesario. He sees Cesario's manners and intellect as being very high above his own. First, Viola as Cesario demonstrates her cultural equality by answering Sir Andrew in return in French. Then, she proves her superiority through the clever things she says as Cesario. For example, she compliments Olivia by praising her scent in the line, "[T]he heavens rain odours on you!" (III.i.81). Viola as Cesario next impresses Sir Andrew by cleverly using the word "pregnant" to mean "expert" or "clever," saying that only Olivia's "expert" ear can hear what Viola has to tell her from Duke Orsino, as we see in Viola's lines, "My matter hath no voice, lady, but to your own most pregnant and vouchsafed ear" (eNotes, 84-85). When Sir Andrew hears Viola as Cesario speaking so cleverly, he quickly recognizes her education and breeding and says to himself, "That youth's a rare courtier," meaning "an aristocrat" (eNotes, 83).
We later learn that Sir Andrew feels insulted by Cesario. Sir Toby brought Sir Andrew into the house hoping that Olivia would accept him as a suitor. But now Sir Andrew sees Olivia paying a great deal of attention to Cesario who, aristocratic as he may be, is only supposed to be a mere servant to Orsino. He feels so insulted that he is resolved to leave, but Sir Toby and Fabian encourage Sir Andrew to challenge Cesario to a duel, saying that it will attract Olivia's attention.
Hence, we see that Sir Andrew admires Cesario, recognizing her to be superior in intellect and breeding, but also feels insulted by her and jealous.