Maria serves the function of uniting the foolery in the play with the more sensible thoughts and actions. She also has a very important role in driving the plot forward.
Maria walks an interesting line between the play's bawdy characters, like Sirs Toby and Andrew, and the more rational characters, like Feste, and the line she walks serves to unite the two worlds. Since the play was written for an Epiphany, or Twelfth Night, celebration and spoofs the type of behavior characteristic of the holiday, Sirs Toby and Andrew are perfect examples of such bawdy, reckless, and lawless behavior you would find on that night. Sir Toby is a drunkard, while Sir Andrew is described as a wasteful, idiotic coward. More importantly, Maria is seen reprimanding their behavior. In the beginning of the third scene, she scolds Sir Toby for his drunken behavior, warning him that Olivia disapproves and that he "must confine [himself] within the modest limits of order" (I.iii.7-8). She even points out that Sir Andrew is a spendthrift and an idiot. Furthermore, she even tries to quiet them down one night when they are getting rowdy in the house, begging, "For the love o' God, peace!" (II.iii.80). Maria's ability to recognize bawdy, foolish behavior and her desires to at least calm down such behavior shows us that while she associates with the bawdy and foolish, to some extent, she herself is actually above the behavior, which also shows us that she walks a line between bawdy and reasonable behavior.
However, she crosses that line when she comes up with the plan to humiliate Malvolio through making him believe Olivia is in love with him. While Maria is enough above bawdy, foolish behavior to chastise it, she is not as strict in her principles as Malvolio. She sees him as an arrogant, pompous "kind of Puritan," meaning that, just like the Puritans who immigrated to America, she sees him as being "overly virtuous and too strict," even judgmental, and she resents him for it (eNotes, II.iii.129). While the prank to write the letter and humiliate him before Olivia is innocent enough, Maria slips into bawdy, unlawful behavior when she goes along with Sir Toby's idea to next lock Malvolio in a dark room as a madman. This is particularly unjust treatment, especially since it is a form of torture. However, since prior to this fall Maria was condoning bawdy behavior, we see that she does act as a link between the foolish and sensible behavior found in the play. In addition, her idea to pull a prank on Malvolio helps move that part of the plot forward.
Sir toby is olivias uncle who lives with her but she disapproves her behaviour and jokes and is tired off his habit to find a match of his own choice for Oli via.maria is a witty waiying woman of Oliviawheras Sir andrew agucheek is friend of uncle tobyand.wants to woo Olivia at any cost.Feste is a clown,a jester whose sole purpose is to provide entertainment.
Sir Toby is Olivia’s uncle. Olivia lets Sir Toby live with her, but she does not approve of his rowdy behavior, practical jokes, heavy drinking, late-night carousing, or friends (specifically the idiotic Sir Andrew). Sir Toby also earns the ire of Malvolio. But Sir Toby has an ally, and eventually a mate, in Olivia’s sharp-witted waiting-gentlewoman, Maria. Together they bring about the triumph of chaotic spirit, which Sir Toby embodies, and the ruin of the controlling, self-righteous Malvolio.
Sir Andrew is a friend of Sir Toby’s. He attempts to court Olivia, but he doesn’t stand a chance. He thinks that he is witty, brave, young, and good at languages and dancing, but he is actually an idiot.
Maria is Olivia’s clever, daring young waiting-gentlewoman. Maria is remarkably similar to her antagonist, Malvolio, who harbors aspirations of rising in the world through marriage. But Maria succeeds where Malvolio fails—perhaps because she is a woman, but, more likely, because she is more in tune than Malvolio with the anarchic, topsy-turvy spirit that animates the play.
As the clown, or fool, of Olivia’s household, Feste moves between Olivia’s and Orsino’s homes. He earns his living by making pointed jokes, singing old songs, being generally witty, and offering good advice cloaked under a layer of foolishness. In spite of being a professional fool, Feste often seems the wisest character in the play.