Twelfth Night — Act 2, Scene 3: OLIVIA's house.

Sir Toby and Sir Andrew stay up late drinking and singing with Feste the clown, enjoying each other’s company and making a loud racket in Olivia’s house. Maria interrupts and warns that Malvolio is angry about their disorder. Malvolio arrives and rebukes them for behaving like drunkards, telling Sir Toby that Olivia tolerates him only if he stops his misconduct. Sir Toby mocks him, and Malvolio storms off. Maria then reveals that Olivia has been disturbed by Cesario’s visit and proposes a prank: she will write fake love letters in Olivia’s hand to trick Malvolio, who is vain and self-important. Sir Toby and Sir Andrew approve, and they all agree to the plan.