How do I tell the difference between a malapropism and a pun in Twelfth Night?I understand what they are. A pun is intentional for laughs, and a...

For most literary works, but especially in Twelfth Night, you have to consider the source of the quote to determine whether the speaker intends to use word play (a pun) or unintentionally messes up his or her language (a malapropism).  For the delivery of puns, Shakespeare normally uses his witty, satirical characters such as Feste.  Even though Feste and other jesters (clowns) are often referred to as "fools" inRenaissance works, for Shakespeare, they speak the truth in a witty manner.  In Twelfth Night, Feste remains objective and separated from all of the mixed-up romances and incorporates puns not only to please Olivia but also to speak the truth cleverly.  Orsino enjoys word play also; so he is another character who introduces many puns throughout the play.

In contrast, characters who are guilty of malapropisms are simpletons--not necessarily in social class, but in their logic.  In Twelfth Night, Sir Toby Belch uses several malapropisms, and it is clear that he is not witty or sober enough to think of puns. Often someone's use of a malapropism illustrates his desire to appear more intelligent than he really is.

So, in general, analyze a character's nature--clever or simple--and you will be able to determine whether he or she intentionally uses word play.