Identity and performance
Almost every character in the play is performing a version of themselves. Viola performs a gender. Malvolio performs a fantasy of status. Orsino performs the role of a suffering lover. The play keeps asking how much of who we are is just a role we decided to play.
Love as self-deception
Orsino loves the feeling of being in love more than he loves Olivia. Olivia falls for a disguise. Sir Andrew pursues someone who ignores him. Shakespeare shows desire as something people often get wrong, directing it at projections rather than real people.
Class, status, and resentment
Malvolio's story is about class anxiety. He wants to rise above his station and is punished for it by people who already have the status he wants. His humiliation is funny to the aristocrats in the play, but the audience is left to decide whether it should be.
Festivity and its limits
The play is named after Twelfth Night, a holiday of disorder and excess. Sir Toby embodies that spirit. But the play also shows the cost: Sir Andrew is used and discarded, Malvolio is destroyed, and Feste's final song is melancholy. The party has a morning after.
Gender and desire
Viola in male disguise attracts Olivia, which raises questions the play never fully answers about what desire is actually responding to. Orsino's closeness with Cesario also sits in complicated territory. The disguise makes visible how unstable gender categories can be.