ULTIMATE NIKKI THEORY!! -Read carefully
Hello guys. I've been wondering the same ever since I saw Nikki. Is she a crazy person or does she belongs to the same league as Peter Petrelly and Hiro Nakamura?
Here's my shocking theory:
Nikki's powers have yet to manifest at their fullest...but she won't allow it.
Multiple personalities are the remaining effects of her TRUE superpower: Mitosis.
As Mark Parkman developed a further stage of his Power, so would Nikki Sanders if not for the traumatic event that prevents her from doing so.
When she was a child, her father abused her and since she was such a meek and quiet child he was sure he could get away with it.
One day out of desperation Nikki's powers Kicked in. Her father found TWO identical girls sitting in her bed, one scared but somewhat exited , the other looked defiantly at her father. The abuse will have to stop.
For unknown reasons, Nikki's dad kept the secret and told a story of how the girls were twins. The truth is that he was too afraid of this new, brave and amazingly strong Nikki named "Jessica"that wouln't let him be his abusive self...so he managed to get rid of her by unknown means (some theories point towards Nikki re-absorbing her by means of hypnosis provided by the Company) and ever since, Nikki has been out of touch with her identity. That's why she allows her other self to manifest in the same body.
Once she gets the true knowledge of her abilities she will channel them to the what she trully is: A Cloner.
Perhaps she can use her dormant mitosis to spawn not two but MULTIPLE Nikkies to handle specific needs. Just as she did before.
Please regard this info as <CLASSIFIED>

