•Why it earns a slot
Twelfth Night is Shakespeare's most fully developed exploration of romantic self-delusion and gender disguise, and the Malvolio plot introduced one of the stage's most enduring comic victims, whose parting threat gives the comedy an unusually sharp aftertaste.
Shipwrecked in Illyria and believing her twin brother Sebastian drowned, Viola disguises herself as a young man named Cesario and enters the service of Duke Orsino, who sends her to woo the mourning Countess Olivia on his behalf. Olivia promptly falls in love with Cesario instead, while Viola falls in love with Orsino, creating a tangle of misdirected desire that only the surprise arrival of the living Sebastian can resolve. A parallel comic plot sees the pompous steward Malvolio tricked by a forged love letter into humiliating himself before Olivia, for which he is imprisoned as a madman before the deception is finally exposed.
This distillation is written from the freely available original, which is always the better read when you have the time: gutenberg.org.