The romance between Viola and the Duke Orsino initially seems a little lackluster and overly convenient; it seems to pale beside the romance between Viola and Olivia. And yet there's an occurrence that Orsino starts off the play as a real Emo Teen with this over-idealized idea about love, and what Viola does — plucky, brave, outspoken Viola — is she shows him that love doesn't have to be this train of sighs and pun-making — it's about friendship and confidence and being happy with someone else, and doing things for the person you love. And suddenly it all fit.
It's strange that Sebastian can defeat not only Andrew, but also Toby so easily - Toby does seem as somebody practical and actually should be a good fighter. But then it occurred to me: he had more experience with brawls than with regular fencing fight, he was drunk, and most importantly, he still assumed "Cesario" was a coward - he completely underestimated Sebastian, otherwise he wouldn't get involved into fight at all!
It's a pondering on why Feste didn't notice that Viola was a girl if he's the smartest character in the play. The teacher said he didn't care, but it was too fun for him to break up. That, and he figured out that she has a reason for it.
Malvolio is a puritan. In Shakespeare's day the Puritans were trying to ban the theatre. So for a playwright and a theatre-going audience, he'd have been much more of an acceptable target than he seems to be today.
Why is Maria able to write very like Olivia, such that Malvolio mistakes her handwriting for that of their mistress? Olivia might well have been the one who taught Maria how to write, and Maria learned by copying Olivia's handwriting.
In the original text and in the productions when Viola joins Orsino's court not just masquerading as a boy but as 'an eunuch' - wouldn't Olivia have noticed Sebastian was pretty much *ahem*, intact?
Cesario is described to Olivia as a boy, and not a eunuch. And it's up to interpretation just what the two of them get up to in between meeting and marrying. It could have just been a lot of kissing and a tour of the grounds.
Another Olivia-and-Sebastian plot hole: how did they get married without the subject of Sebastian/Cesario's name coming up?
It's been imagined that she kept calling him Cesario and he kept saying, "that's not my name" but she refused to listen and in the end, because of the absurdity of his situation and his loneliness he just went with it.
There's also the possibility that she just kept calling him things like "my love" and such, never actually referring to him by name.
It actually does come up: Olivia calls him "Cesario" when she first sees him and he never says anything about it. Given that Sebastian has a monologue (albeit a brief one) that essentially amounts to him saying "I have no idea what's going on - whether I'm mad or she's mad or the entire world is mad - but I've got the most beautiful woman I've ever seen throwing herself at me and I'd be an idiot to pass this up", it's very likely that he just never actually bothered correcting her certainly before or during the ceremony; whether he even bothered to try and set her straight is up for each individual production to decide but the clear implication judging from Olivia's behaviour once Viola shows up is that Sebastian hasn't bothered to try and correct her at all and has just been enjoying the benefits of the situation. Some productions even specifically have Olivia reacting in shock when Antonio calls him "Sebastian".
