The genius of Twelfth Night is Feste, the most charming of all Shakespeare’s fools, and the only sane character in a wild play. Olivia has inherited this court jester from her father, and we sense throughout that Feste, an accomplished professional, has grown weary of his role. He carries his exhaustion with verve and wit, and always with the air of knowing all there is to know, not in a superior way but with a sweet melancholy. His truancy is forgiven by Olivia, and in recompense he attempts to charm her out of her prolonged mourning for her brother. Feste is benign throughout the play, and does not participate in the gulling of Malvolio until he enters the dark house as Sir Topas. Even there, he is instrumental in bringing about the steward’s release. A superb singer (his part was written for Robert Armin, who had an excellent voice), Feste keeps to a minor key.
(page 244)