The concept of mistaken identity is a favourite motif for Shakespeare. Such mistakes create tangled situations and helps in the complication of the plot.
In the play Twelfth Night the problem of mistaken identity arises from the disguised gender. Viola, a young lady, dresses herself as a man. Thus she looks exactly like her brother Sebastian. This situation creates a mess. Viola falls in love with Orsino but cannot express her feelings because Orsino thinks her as a man. On the other hand, Olivia, who is the object of Orsino’s affection falls in love with Viola, who is dressed as Cesario.
Confusing situations are created when Viola’s brother Sebastian comes into the same environment as Viola. Olivia believing that Sebastian is actually Cessario asks him to marry her. Sebastian overwhelmed at the situation but attracted by the lady’s beauty accepts the proposal. This irritates the Duke who accuses Cesario of ingratitude. Thus there are a number of deceptions resulting from the problem of mistaken identity.
The problem was solved in the end. After getting married, Sebastian wanted to give the good news to his friend Antonio. But Antonio was taken as prisoner. When the Duke arrived with Viola dressed as Cesario Antonio told how he rescued this youth and so he charged him for being ungrateful. The Duke on the other hand, dismissed Antonio’s story declaring that Cesario has been with him for the last three months. But the Duke was extremely angry hearing Olivia’s love words for his page and threatened him (her) with death. Viola, as she loved Orsino would have joyfully accepted death to give her master ease, but Olivia was not ready to lose her husband. At this moment Sebastian, another Cesario arrived at the spot. They looked alike and Viola acknowledged that she was a lady in disguise of a man.
Thus the errors got cleared up and Orsino proposed marriage to Viola. The twin brother and sister got married on the same day and the story ended happily.