I need to start off by saying, She's the Man is an AWESOME MOVIE! So funny. I have to note, however, that there are quite a few differences between the original play and the modern spin-off. Here's a quick list of notable differences:
1. A number of left out characters! Including:
*Antonio: A friend of Sebastien's, develops a sort of romantic attachment to Sebastien.
*Malvolio: Yes ladies and gentlemen, he's a person. Not a spider!
*Sir Toby: Olivia's drunkard uncle. He is pushing for Sir Andrew Aguecheek to court Olivia.
*Maria: Oliva's lady-in-waiting.
*Feste: The fool of the play.
2. Olivia refuses Orsino's love because she is mourning the loss of her dead brother.
3. Viola thinks her brother Sebastien is dead, but is hoping for his return.
4. Sir Andrew challenges Cesario (who really is Sebastien) to a duel over the right to Olivia, and it is during this duel that Olivia proposes marriage to Cesario.
5. Malvolio is the focus of a prank masterminded by Maria (Olivia's lady in waiting). Malvolio is given a letter that is supposedly from Olivia. He is tricked into thinking that Olivia is in love with him, and taking extreme measures to prove his love back to her. Olivia thinks Malvolio has gone crazy, and has him imprisoned. This prank is actually a central part of the play.
6. Maria (Olivia's lady-in-waiting) and Sir Toby (Olivia's uncle) get married at the end of the play.
There are many more small deviations from the storyline, however I feel that this encompasses the largest of the differences. I'd be interested in seeing a video production that fits more closely to the actual play. I do have to say though, that She's the Man still holds a special place in my heart. :)
