1.1.1: Duke Orsino listens to music and talks about love.
1.1.2: When Curio asks Orsino if he's like to go hunting, Orsino tells us how he felt the first time he laid eyes on Olivia.
1.1.3: When Valentine informs the Duke that Olivia is mourning for her dead brother, Orsino says Olivia will be a great lover once she falls in love.
1.4.2: Orsino says that since he's shared secrets with "Cesario," his boy page should be the one to woo Olivia on his behalf.
1.4.5: Orsino describes "Cesario's" luscious mouth, voice, and throat before sending "him" off to Olivia's.
2.4.1: The Duke discusses love with "Cesario." He warns "Cesario" to marry a younger woman and says that women's beauty fades, just like men's interest in them. Then he says that women are incapable of love and listens to "Cesario" tell a story about a woman who kept her great love a secret. He sends "Cesario" back to Olivia's house.
5.1.1: Duke Orsino talks with Feste in front of Olivia's house.
5.1.12: When Antonio is brought by in handcuffs and accuses "Cesario" of being deceitful, Orsino defends "Cesario. Orsino recognizes Antonio as a pirate who stole from him.
5.1.15: When Olivia returns home, Orsino hits on her but is rebuffed.
5.1.17: Orsino blows up when he thinks that "Cesario" has hooked up with Olivia. He storms off and "Cesario" chases him.
5.1.19: When Olivia claims to have married "Cesario," Orsino is devastated.
5.1.24: When Orsino sees Sebastian and "Cesario" together, he's amazed and can't believe his eyes.
5.1.26: Orsino is excited to see Viola in her dress once he learns that she has been disguising herself as "Cesario."
5.1.30: Viola can't change into her dress just yet – the sea captain has her clothes. So, Duke Orsino says he'll marry Viola after she changes. Until then, he'll call her "Cesario."