Final answer:
In Twelfth Night, Malvolio commits a malapropism by smiling constantly due to a misinterpretation, demonstrating dramatic irony and humor in the play.
Step-by-step explanation:
An example of a malapropism in William Shakespeare's Twelfth Night occurs when the character Malvolio follows Olivia's supposed instructions to smile constantly to show his delight, misinterpreting her distress as a sign of affection. Instead of interpreting Olivia's frown properly, he assumes a disconnected smile is what's required, thereby using his expression inappropriately and confusing the action's intent with the emotion it should convey. This malapropism showcases the dramatic irony and the humor in miscommunication.