Twelfth Night is one of Shakespeare's best plays, which challenges ideas of heteronormativity and strict gender roles. The characters transcend the limitations that are placed upon them by society.
At the time when the play came out, people believed in conformity to assigned gender roles. Women were not supposed to dwell in public spaces, and it was considered immoral for a woman to act in a theatre. All roles were played by men, with female roles being acted by younger boys. When Shakespeare wrote a female character that dressed as a man, he created an unusual complexity: viewers would find a man (the actor) playing a woman (Viola) who pretends to be a man (Cesario).
Cross-dressing was an important theme in the play as Viola dresses up as a man to survive in the town she is stranded in. Just by changing her clothes, she becomes a different person, and everyone sees her as Cesario (Shakespeare did not reveal her name till the disguise was removed). This shows how gender roles are nothing but social constructs, so they are performed rather than being natural. Changing one's voice or clothes allowed them to take on a different identity. Viola and her twin, Sebastian, look the same (hence the confusion). Their interchangeability shows how the gender binary is merely a vague, ambiguous distinction.
Homoeroticism was another significant theme in Twelfth Night. Viola (a woman) loves Orsino (a man), but Orsino expresses his affections even when she is disguised as Cesario. As Cesario, she goes to Olivia (a woman) who almost instantly falls for her. Orsino sends Viola/Cesario as a messenger, but the speech he has prepared to woo Olivia is inadequate, so Viola has to re-write and deliver it (causing Olivia to fall for her). This challenges the notion of heteronormativity, as we see a woman discarding the words of another man, and instead articulating the words that will effectively woo another woman.
The title of the play refers to the Twelve Nights of Christmas, during which people are busy in festivities and celebrations, so they do not completely adhere to the social roles assigned to them. At the end of the play, the 12th night is over, and order is restored, with disguises coming off, and the women marrying men.
Like many of Shakespeare's contemporaries, Pakistani readers might not be familiar with the themes raised by the play. Many people find the complexities created to be offensive, as the homoeroticism is not subtle, and characters visibly cross-dress to challenge stereotypes. For these viewers, the ending comes as a relief as the characters return to their socially determined roles. However, the play does leave a lasting impact on its audience, who might be forced to rethink their biases and assumptions about the world.
(Note: in case you haven't watched or read 12th Night, "She's the Man" is based on it)
Pictured: Olivia and Viola (dressed as Cesario) in the 1996 film adaptation.