We have all seen the new Batman v Superman: Dawn of Justice trailer right? No? Then where were you?! In the Grand Canyon?!
Anyways, I saw a bunch of new confirmed details in the trailer and I came up with an interesting theory. Remember, this is just a fan-theory, not actually confirmation of casting or storyline.
It was revealed in the trailer that Holly Hunter is to be playing an original character, known only as a senator who goes to Lex Luthor for support in her debate against Superman. But one mystery character who was not revealed, was that of Hunger Games: Catching Fire star Jena Malone. Fans have theorized that because parts of the plot are taken directly from Frank Miller's The Dark Knight Returns Part 2, that Malone would be playing the role of the Carrie Kelley version of Robin. But this has yet to be confirmed. After seeing today's trailer, I have thought of an interesting theory regarding Malone's character. My theory goes like this:
Lex Luthor has 2 things: A piece of Kryptonite, and the body of General Zod. Luthor wants Superman gone but can't beat him on his own. So he thinks of a way to use Zod's DNA and the Kryptonite in order to create his very own Kryptonian warrior; one that will only work for Luthor unlike Superman working for no one. After a trial run, he succeeds in creating his very own Superman clone, but, being Luthor himself, he wants it to look more like something he would enjoy having around; such as a beautiful young woman.
My theory is Jena Malone is playing the role of Kara Zor-El, also known as Supergirl! Supergirl is Superman's Cousin who also escapes Krypton at the same time he did. But since the DC Extended Universe is going to be a bit darker, why not change her story. Instead of Supergirl being Kal's cousin, I predict that she is created by Luthor to serve his purposes.
While she is in the final stages of re-animation, Luthor gets impatient and decides to make another clone using all of Zod's body and the rest of the Kryptonite, in order to create an even stronger clone in case Supergirl fails. But as he is waiting, Superman, Batman, and Wonder Woman break into Luthor's lab to try and stop him. Because of this the experiment goes haywire and Zod transforms into Doomsday.
Doomsday makes a rampage in Luthor's lab while Lex hides like a coward and Superman makes off with an unconscious Supergirl.
To some people this would make a lot of sense, but to others this may seem a little far-fetched; I say to each his own. If you agree, agree! If you don't agree, then don't!