Maybe it just strengthens the eyes then? *shrugs* Hell, maybe the mako counter-acts the degrading of their eyes that happens with mangekyou use?
Who says they could stop Zack? He'd be ANBU material, I have no doubt. So if he and Itachi hung out during their ANBU period, who's gonna stop them?
And on the AU thing, if Zack leaves the Uchihas before Itachi can remember him being an Uchiha, he'd likely have to leave before Itachi was around 3, max. That's when the first memories start forming.
HAH. Sasuke would totally recognize Kakashi's behaviour, as it'd resemble his own fanclub's reaction to him. And it'd be different from Hinata, mainly because Kakashi'd be able to keep his cool for the most part, just get a bit... er, nervous? Jittery? I donno, something, when Cloud's around. ... oh hell, just got to wondering, which reaction would be better. Kakashi meeting Jiraiya or getting to talk with his crush? ... I'd rather think the second, actually, since he likely grew up with Jiraiya, considering who taught him.
Hrm. Genin teammates tend to be in the same school year, though. So unless Aerith and Cloud graduated early, or Zack was somehow stuck at Genin for the two years or so for.. them...
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*facepalm* And... I'm an idiot. If Cloud is gonna be old enough to adopt Naruto later (which means he's gotta be old enough - and with enough of a reputation - to take on and WIN against the Council Elders), then that means they're graduating during the war with Rock. Which means they were likely shoved out of the Academy ASAP, to kill or be killed. It wouldn't be unheard of for Zack to be the sole survivor of his team, and why wouldn't two recent grads be put with him to get a working team back going? That being said, I can see Sephiroth or Vincent being their jounin instructor. Most likely Sephiroth, because Vincent would be busy being ANBU or a Hunter-nin. *grins*
Aerith would totally be related to the First, given her ability to grow plants anywhere. =D