Twelfth Night, or What You Will
Duke Orsino, who rules over Illyria, is the object of Viola's affection. He also claims to be in love with the Countess Olivia. (He's not really in love with Olivia – he just thinks he is. He's also in love with the idea of being in love.) Orsino doesn't know (or pretends not to know) that Viola is disguised as his boy servant, "Cesario." Even though Orsino thinks "Cesario" is super-cute and loyal and all, he doesn't really entertain the idea of "Cesario" being a serious love interest. But when Orsino learns that "Cesario" is really a woman, he jumps on the chance to marry Viola.