what are the functions of disguises and mistaken identity in twelfth night?

Typically mistaken identity and disguise in a work serve to heighten humor, create dramatic irony (the audience knows more than the actors on stage so it can be more intense) and to have characters reveal their true feelings on a particular topic. In Shakespearean comedies especially, the humor, etc., is never hurtful, but rather helps build suspense and then leads to a satisfactory ending.

Disguises and mistaken identity are used in Twelfth Night as a source of confusion.