In another room of Olivia's house, Sir Andrew tells Sir Toby that he has finally decided to give up and leave because he saw Olivia flirting with Cesario in the orchard. Sir Toby assures Sir Andrew that Olivia was only trying to test his valor, and that to impress Olivia, Sir Andrew should now challenge Cesario to a duel. Persuaded, Sir Andrew goes off to write a letter of challenge. Sir Toby promises to deliver it.
Spying on Olivia and Cesario, Andrew acts as the audience to their courtship "performance." From here on out, the subplot involving Andrew and Cesario parodies another conventional ritual of dramatic love: the duel.
Once Sir Andrew has left, Sir Toby admits to Fabian that he only wants Sir Andrew to hang around so that he can keep leeching off of him.
Another performance: Toby, Andrew's supposed friend and ally, is deceiving him.
Maria arrives, and tells Sir Toby and Fabian that Malvolio is doing everything instructed in Maria's letter, and making himself entirely ridiculous in the process. Maria comments that Olivia will probably hit Malvolio for his idiotic behavior and that, when she does, Malvolio will simply smile and consider it a sign of favor. Sir Toby is delighted.
The over-the-top drama of the prank on Malvolio, which causes Malvolio to make himself look absolutely ridiculous for the sake of love, echoes the Orsino-Viola/Cesario-Olivia love triangle and forces the audience to see how love makes those characters also act in silly ways.