My theory continues to be (and I've seen nothing to contradict it) that Niki/Jessica are one person with a split personality caused by her father's abuse. Nothing powers-y about it. That the strength initially could be tapped only by "Jessica" was a result of her psychosis and nothing more.

That's always been my take on it too, Jon.

something about the way the father talked about Jessica led me to believe they were two separate people, but it's been so long since i've seen it i could be wrong.

oh and i thought it was complete crap that Candace's "true form" showed up when she "died" (quotes because i'm still not positive she's actually dead) too. she was knocked out in the finale last year. why didn't she revert back to that form then too? she would have no control over her powers if she was unconscious.

I thought I remembered seeing Jessica's grave, but I have the same been so long since I've seen it problem as tiggy.

I thought I remembered Jessica's grave too, but am only saying now that amych said it first so I don't look crazy (because I have a bad memory for details).

As for Candace, yeah, I agree with what tiggy said. I thought that the weight thing was either a) a nod to the fans who caught her original comment or b) a way to signal she was "dead" (not sure if the signal was for us or maybe Sylar).

I don't remember a grave, but I do remember their father speaking as if he had two daughters.

Well, could there have been two daughters but one died in such a traumatic event (trauma to both) that the split that developed in Nikki's personality took on the persona of her sister?

The fact that Jessica actually existed doesn't exclude the possibility that Niki has a split personality.

Yeah, they had the dad tell Jessica that she was dead, and Niki went to her grave. But Dana's right that this doesn't negate the split personality theory. I think they're going with the split personality as a power, though, what with Peter talking about how much he wanted to Darth Vader the Irish guy to death and then camera showing the godsend tattoo disappearing from his arm.

There were two daughters. One died, at the hands of their father's abuse, and the other developed a multiple personality -- which happens to have the same name as her sister, although the real Jessica was young when she died, so it's doubtful the personalities are similar at this point.

Adopting the persona of a dead sibling -- one who was seen as a "protector" -- strikes me as not unreasonable for a personality that emerges to "protect" the real person. Indeed, without looking it up, I'd be amazed if it's unprecedented.