Nearly every character in Twelfth Night adopts a role or otherwise disguises his or her identity. Viola disguises herself as a man upon her arrival in Illyria, setting the plot in motion.
Viola's patient and self-sacrificing love for Orsino helps the duke to reassess his own artificial and self-indulgent love of love. Viola's observations about the destructive influence of time and melancholy on youth and beauty have been compared to similar remarks made by Feste. In I.v.241-43, for example, she upbraids Olivia for wasting her beauty by leading it to the grave rather than marrying and transmitting her beauty to her children. In II.iv. 110-15, thinking of her own hidden love for Orsino, Viola paints a vivid picture of the effects of time and unrequited, unproclaimed love on the "damask cheek" of a maiden who "sate like Patience on a monument, / Smiling at grief."
It has also been pointed out that Viola can be fatalistic in her attitude to time. When she discovers that Olivia has fallen in love with her, Viola/Cesario pities the countess, but concludes that time "must untangle this, not I / It is too hard a knot for me t'untie" (II.ii.40-41).
Interestingly, unlike other Shakespearean female characters who adopt disguises, Viola does not remove her men's clothing at the end of the play, and the rest of the characters, including Duke Orsino, are left to take her true identity on faith.