Viola, pretending to be Cesario *a made-up person* (in love with Orsino)
Lady Olivia (in love with Cesario)
Duke Orsino (in love with Olivia)
Sebastian, Viola's twin
Antonio (Sebastian's friend)
Maria (Lady Olivia's lady-in-waiting)
Clown/Fool/Feste (works for Lady Olivia's family)
Malvolio (Olivia's servant)
Sir Toby Belch (Olivia's uncle)
Sir Andrew Aguecheek (Toby's friend)
Captain (Saves Viola and disguises her as a man)
Sebastian and Viola are shipwrecked on the coast of Illyria. The captain helps Viola disguise as a man, Cesario, so she can be Duke Orsino's page. Orsino sends Cesario to Olivia to attempt and woo her out of her mourning for her dead brother; meanwhile, with Sebastian, he's saved by a man named Antonio *who is apparently wanted by the Duke's court, and helps him despite it being dangerous for himself*. Olivia ends up instead falling in love with Orsino's "messenger," Cesario, which gets the confusing love triangle of Twelfth Night started. Viola falls hopelessly in love with the Duke and Olivia's servant, Malvolio, is tricked by Sir Toby Belch, Sir Andrew Aguecheek, Maria, and Fabian into believing that Olivia is in love with him- he's then locked away for being presumed "mad." Sir Toby decides to deliver Andrew's duel challenge to Cesario in person, and the two of them prepare to fight fearfully. Antonio encounters them and comes to Cesario's defense, thinking that Viola is her brother. He's immediately arrested by Orsino's guards, and meanwhile Feste (the fool/clown), Sir Andrew, and Sir Toby find Sebastian and attack him (mistaking him for Cesario). Feste summons Olivia who again proclaims her love- only it's to Viola's twin, not Viola. The play ends with them happily married- Sebastian and Olivia, Viola and Orsino.
The main theme which is the most well-known is love as a cause of suffering. Throughout the play, Shakespeare illustrated that love can cause people intense despair and pain, and that some of the characters even view it as a curse. Love can motivate people to be violent, such as Orsino threatening Cesario, believing that his page had betrayed him to woo Olivia himself. Antonio and Malvolio are the only ones who didn't get their "happy ending." It wouldn't be socially acceptable for a servant to marry a lady of high status, and as for Antonio, he was haplessly obsessed with Sebastian.
Deception, and its consequences, are another slightly more subtle theme. Although disguising herself as a man to protect herself is definitely safer than entering foreign territory as a solitary young woman, this disguise sets a messy love triangle ablaze and puts Olivia, Viola, and Orsino in misery- as well as putting Viola's life in danger when Orsino threatens her for taking Olivia. And Feste is wearing a disguise himself; the mask of a fool. As the play progresses, we're shown that he's actually the most intelligent of the bunch. He played a major part in the plot to trick Malvolio and had the wittiest comebacks of them all.
Gender and sexuality are fluid and malleable in Twelfth Night- Viola in fact technically disguises herself as a "eunuch." Young men would at times have to be in positions where they're intimate with a woman, and by saying that she's a eunuch, she'd be viewed as not a man and not a woman, and she'd be refusing to follow binary norms.
Malvolio's "bad ending" is a warning to the viewers of Twelfth Night to not let ambition cloud common sense and logic; because of his overpowering desire to elevate his status and be in charge of everything, he ended up alone and fell victim to all of Sir Toby, Andrew, Maria, Fabian, and Feste's pranks on him.
To wrap things up, Twelfth Night was a captivating, comical read- the use of intelligent wittiness is what makes Shakespeare’s humor so amusing. It's also what gave the movie a slight downside. It was easier to read the mood of the environment when I was watching the play, but easier to comprehend the jokes in written format- most of the time, they're a bit complex and need some thought before you can realize, "Oh yeah, that's actually funny!" (Speaking of the movie...who on Earth picked the thumbnail for the Bonus Scenes section? ? It looks like if you just forgot to lock the bathroom and someone else comes in.) The plot for the written format was definitely confusing and I had a hard time keeping track of the things going on, but the end cleared everything up and tied things up neatly.