I think in the comics, Jean was posessed by the Phoenix Force, which might have come from space... I'm not quite sure. But obviously, they aren't going to throw in some space anomoly into the movie versions, so they found a way around it, which is similar to what was going on in Ultimate X-men.


The extra scene at the end of the credits had(SPOILER) Moira enter the room of that comatose guy Xavier was talking about in the beginning of the movie, and he mutters in Xavier's voice "Moira..." or something like that and she looks at him all wide eyed and says "Charles...?" and it ends. Basically it's a safety net in case a sequel were to be made. It kinda cheapens Xavier's death, though...