act III, scene IV
* Mistaken Identity due to a specific behavior- (Malvolio is taken for a crazy person)
Malvolio behaves as a mad and fool man due to the letter that was written and sent to him on behalf of Olivia; however, she knew nothing about the letter so she couldn't understand Malvolio's behavior and she sends him with Sir Toby and Maria (who wrote the letter) so that he can have a proper treatment for his craziness. Malvolio is taken for a crazy person when he was only acting like crazy due to the letter.
*Mistaken identity due to a disguise - Viola disguises her as Cesario, a man.
Andrew and Cesario find each other and they take out their swords to fight a duel but Antonio sees this situation and decides to fight Andrew instead and free Cesario of this fight because he thinks Cesario is his beloved Sebastian (Viola's twin brother).
act IV, scene I
*Mistaken identity due to a disguise - Since Sebastian and Viola are twins, there is a confusion.
The clown Feste finds Sebastian and he mistakens him for Cesario and tries to take him to Olivia´s house. Sebastian gets mad for this confusion and when Sir Andrew and Sir Toby appear, Sir Andrew takes out his sword and tries to fight him since a few minutes ago he was trying to do that, but Sebastian is very good with the sword, not like his sister Viola (disguised as Cesario) and he makes the noble man beg for his life.
act IV, scene III
**Mistaken identity due to a disguise - Viola disguises her as Cesario, a man.
Sebastian is at Olivia´s house and she confuses him with Cesario (who actually is Viola in a man disguise) and he is very confused because the beautiful Olivia is asking him if he still wants to get married with her and he says yes so both of them go to the priest and get married.
act V
*Mistaken identity due to a disguise - Viola disguises her as Cesario, a man.
Viola and Orsino arrive to Olivia´s house and also Antonio arrives with the law officers and he confuses Viola as Cesario for Sebastian and he accuses Viola to have stolen his purse and denied to know him.
*Olivia enters in the scene thinking that Cesario is betraying her by telling Orsino that she is in love with him when they just got married. Orsino takes Cesario (Viola) to be killed for this betrayal when the one that got married to Olivia was Sebastian.
* Sir Andrew and Sir Toby also accuse Cesario(Viola) of attacking and injuring them, but Cesario did nothing, it was Sebastian who attacked them.
* Sebastian arrives to Olivia´s house asking for forgiveness from Olivia for having injured Sir Andrew and Sir Toby and for the first time, the twins get together and start talking about all the identities, disguises and confusions.
