Oh my God, that's it! Zack's still in iraq and is wondering why no one calls him to say hi That's why he's been acting so strange; hey, do you think that shapeshifters can change their voice? 'cause if not, the Apprentice is a really good singer (I'm thinking "eew" as I write it, 'cause I hate opera music) and pretty strong. Another explanation is that the Apprentice kidnapped Zack around the Verdict in the Story and has been impersonating him ever since. So maybe zack's hands aren't hurt at all and the Apprentice got a kiss from Zack's love Brennan instead of Zack!
So Cam's from Pluto... When I was thinking where she could be from, I was particularly thinking about her eyes (I never noticed them until you mentioned them), where would be a proper place for them. i actually didn't know that Pluto's been demoted, but I was watching Spaceman in a Crater today (I just love Hodgins in this episode!) and Hodgins made it pretty clear...
It depends on whether they change their actual morphology, or if they only alter the perceptions of those who see them (through mind-control or tricks of light). If they can actually shapeshift then, assuming they become a perfect replica of the victim (including the structures pertaining to speech), their voices should match the victim's as well.
Maybe Hodgins' pushing the painkiller button was some sort of secret alien-test, to see "Zack's" reaction to the medication. Maybe he knows the truth, now. Watch out, Hodgy.
I feel sorry for Pluto. I wonder if Cam's doing anything to try and re-establish its status, or if she's devoting all her energies to getting Booth, thus solving at least her problem.
Jupiter's pretty big, she could probably bring all of her Plutonian acquaintances along with her....