In this video from Penn State's School of Theatre production of Twelfth Night, Feste, the clown, enters Olivia's house. He sings a song; Sir Toby and Sir Andrew join in. Maria comes along to stifle their rowdiness and warn the men that Olivia is sending Malvolio to quiet them down.
Shortly thereafter, Malvolio arrives, insults Sir Toby and threatens to tattle on Maria to Olivia. Maria and Sir Toby are riled up by his behavior toward them. She intends to forge a love letter from Olivia to Malvolio, and she recruits Toby, Andrew, and Feste to help with the joke.