One of the most overt examples of disguise is through the character of Viola. This is the origin of much of the deception in the play. Stranded in Illyria after a shipwreck, she dresses as a male in order to work as a Eunuch for the Duke Orsino.
'Thou shall present me as an eunuch to him' (Line 58, Act one, scene two). This is the first accidental deception and is where the disguise forms the plot. Viola does not intend to deceive people, as her original intentions were to get a job with Orsino, however the disguise constructs the plot and the romantic deceptions with Olivia, Orsino and Cesario.
The relationship between Olivia and Cesario is based around disguise and deception. For example, Olivia is deceiving herself by thinking she can mourn for her brother and abjure the company of men. This deception is gone when she shows interest in the young man at her gates in I.5. But a new type of deception is formed by Viola’s disguise. Viola is deceiving Olivia by disguising as a man, making Olivia fall in love with a man, who is in fact a woman. By doing this, Shakespeare is creating multiple confusion, because in Elizabethan theatre, a man would play the role of a woman and the woman (Viola) disguised herself as a man.
The play begins with a striking example of self-deception, initially amusing for the audience, in Orsino's declaration that he loves Olivia. Orsino's sense of superiority ('my love, more noble than the world' - II.4.80) leads him to the assumption that he has a ‘true place’ in Olivia's favour