Disguise and how it is used in comedy
In act one scene one Olivia seems to want to disguise herself to the point of disappearing: her pain is that great. She, like Viola, lost a brother, and she wants to devote her entire being to his memory. She tries to use her body to mourn for him ("watering" his memory with her tears) and almost seems to be punishing herself by covering her face and staying away from other men. In the second scene Viola, for unexplained reasons, wants to escape from the world, so she decides to pretend to be a lowly male servant. Interestingly, she takes on this new, very different identity partly because she identifies strongly with Olivia, who is a woman with a similar temperament to her own. In the fifth scene, the clown disguises himself as an idiot, but no one is entirely fooled. He seems to enjoy countering a seemingly ridiculous statement with one that appears profound. He is thus able to live as a fool while entertaining intelligent people like Olivia and Maria. The clown disguises his real and reasonable advice to Olivia in a speech that seems to make no sense. He effortlessly combines puns and wordplay with true wisdom, and plays the clown while also commanding respect from Olivia (he is supposed to be her lowliest servant, but he is giving her advice.) She tries to send him away, but she also calls him "sir." Olivia wishes to disguise her love for Cesario, so she tells Malvolio that Cesario left the ring with her, when she is in fact giving Cesario her own ring as a token of love. She assumes that Cesario will understand what she is doing and come back to woo her in secret, even though his job is to woo her on behalf of the Duke. Though she is unafraid to be honest about her feelings for the Duke, she is apparently uncomfortable with proclaiming her new feelings for Cesario.
In act two scene oneSebastian says that he and his sister looked remarkably similar, and since Viola has disguised herself as a man, she now (unbeknownst to any of them) looks exactly like him. This will account for much of the comedy later in the play. Mistaken identity and gender confusion are, of course, integral to the way the play develops. In scene four because of her disguise as Cesario, Viola is able to make a poignant speech about love and the nature of women. Orsino, a man, claims to understand women, saying that they are incapable of loving someone as deeply as men are. Viola knows this isn't true, because she has listened to Orsino complain about his love for days, while suffering silently herself. She tells Orsino that men might be more vocal in their declarations of love, but women are just as affected by love as men are. Her speech is all the more effective because Orsino doesn't know who she is, but the audience does.
In act three scene one Cesario sees that the clown, who plays a fool though he is surely wise in some ways, has more freedom than most people at court. A wise man who falls into foolishness is easy to criticize, but a fool who is sometimes wise is looked upon as very entertaining and even admirable. Thus the clown, who is probably just a normal man, acts like a fool and gets respect for it that he might never have had otherwise. In the fourth scene Viola's disguise has made her look exactly like her brother. Interestingly, the one who reveals this fact (thus unravelling both Viola's disguise and her separation from her brother, as well as Olivia's love for her and her love for Orsino) is Antonio. Antonio is perhaps the most constant, honest character in the play. While most of the characters treat their friends and lovers as means to an end or as part of a joke, Antonio loves Sebastian, and feels deeply betrayed when he thinks Sebastian has used him. His feelings are perhaps the deepest and most true of all the characters, (he never hides them) so it is no surprise that he ends all of the jokes and disguises. In the second scene while the other characters have disguised themselves for some purpose, both Malvolio and Sebastian have become "disguised" against their will. Malvolio has made himself appear to be a madman, and he acted the part so well that now he cannot convince anyone that he's sane. Sebastian, because he looks so much like Viola/Cesario, has been beaten, and has gotten Antonio sent to prison without any money. Both men are unable to change their situations or even understand what is going on, because they do not even realize they are disguised.