When Oskar was peeking on Eli changing and saw what looked to be a vagina with a scar. I was wondering what the significance of that was... was it just another weird thing about her? Or was there something else? I'm guessing I probably missed something.

I figured "I'm not a girl" meant "I'm a vampire" uh...

scar on the vagina, and also assumed that the "I'm not a girl" part indicated that she was a vampire. Of course, now that I know there's a scar there, a whole new can of worms has been opened.

"The Dark Knight"

So what's the scar on her vagina?

i think it is because vampires have no need for reproductive or urinary systems, so it was probably genitally mutilated as a custom or perhaps self-mutilated as an indication that she wasn't truly a she or dried up as part of the vampiric process and then sewn up

That wasn't a vagina. That was a scar from when HIS dick was cut off and he was made a EUNUCH. She is a HE. http://en.wikipedia.org/wiki/Eunuch

Eli's full name is Elias. Some time after his genital was removed he started using the name Eli since he now felt he had no gender. The book first starts of as Oskar's point of view and he believes Eli is a girl up until he sees him naked. Then the book shifts and is told from Eli's point of view. From then on the book refers to him as a he. Oskar's hesitation with Eli is more or less explained in the terms that he doesn't want to be gay.

Another reason I doubt those people have read the book is the fact that Eli did not castrate himself. At one point in the book Oskar sees Eli's past through a flashback when they kiss. In the flashbacks (200 years ago) he sits at a table with some other children having a meal. A man with a wig sits also sits at the table. He's drinking something resembling blood.

Eli's mother is also there standing against a wall. The man throws 2 dices, and then counts all the children according to what the dice says. The two dices show 4 and 2 meaning the fourth child from one side of the table and the second from the other. The boy next to Eli is number 2. For some reason the man still picks Eli. When he does this the dice magically changes to 3. We're never told why.

At this moment his mother, visually distressed and crying makes an attempt at grabbing him in order to escape. She doesn't succeed and Eli is taken to another room where he's strapped to a table with a hole in the middle. A guy with a disgusting grin on his face takes a bowl and cuts off his genitals and lets the blood pour down in the bowl. The man in the wig drinks the blood from the bowl. The word genital is used in plural to describe that it's both his penis and testes that are cut of and not to make it more ambiguous. I must admit though that I have no idea what exact word is used in the English translation as I’ve only read the book in Swedish.

I just read just now that the director of the film views the character as something in between. He changed that aspect for the film.

I thought the love story between Oskar and Eli reminded me of The Crying Game. The connection and intimacy between the two kids seemed the same as the connection between Stephen Rea and Jaye Davidson. Like others, I assumed the line "I'm not a girl" meant Eli was a vampire. I never would have guessed Eli's "father" was some pedophile.