Quote Originally Posted by TheAbominatrix
JENOVA cells make a person hard to kill, but being shot point blank in the head multiple times is more than enough to do the job.
Yeah, imagine the end of Resident Evil 3 and replace Nemesis with Zack.

I'll just throw in my two cents here. JENOVA cells have the ability to change one's appearance as well as one's thoughts and memories. When Cloud met Tifa in Midgar after Zack died, what was left of his consciousness remember his want to impress Tifa and be this person that he wanted to be. The JENOVA cells reacted to that, and made him a SOLDIER. It gave him the strength of a SOLDIER, the mako eyes, and in this process it put the memories of Zack, a SOLDIER, in place of Cloud's own memories because those were the memories of a SOLDIER, which the JENOVA cells made him be. So I think that when Cloud is having Zack's memories, he isn't doing it on purpose, the JENOVA cells are making him do it, and Cloud actually believes that these are his memories. So basically everything TheAbominatrix said but with JENOVA cells invoking the whole mess.

Quote Originally Posted by MistaCloudStrife
ALSO.... i read about someone saying that Zack didnt get affected by JENOVA cells.... actually Cloud was supposed to be the one that wasnt affected.... thats why Hojo called him a failure... he was the one who wasnt supposed to be effected... BUT... IMO... i think that Cloud was effected by JENOVA, but instead of reaching his potential in a short time... his potential would be reached slower than others but the end result would be greater than that of a normal person... basically i think the strength from the J cells would effect him slower but in the end stronger... ^_~ Make sense?

Thats why he was the only one that made it to the reunion... he was (in the end) the strongest... out of all of them....
Since we are throwing around theories here, I throw this one out. Now, the threat from the sky, i.e. Jenova, caused a crater that the earth is trying to fix. It's been there for a few millenia and the earth still hasn't fixed it. Why is it taking so long??? Because that's not all the earth is trying to fix. It is also trying to rid itself of JENOVA, until recently. So the earth is using the lifestream to rid itself of JENOVA. JENOVA must either multiply at a steady rate or be rather resiliant to have lasted for so long. So take this down to a smaller scale. To ward off a JENOVA cell, one would need the lifestream, or mako energy. So think of mako energy as like medicine for JENOVA cells. Now, normally when one takes medicine, one already has the systems of the illness. You take the medicine, the symptoms continue until the medicine kicks in, if it even works. However, if you have taken the medicine before hand, i.e. a vaccine or preventative medicine, then your body is ready for the illness before the illness is even there, and it can ward it off without symptoms. So, this is why I believe that Zack was unaffected by the JENOVA cells. He was infused with mako energy to make him a SOLDIER, so in essence he had taken the vaccine for JENOVA cells. It's not said that Cloud is treated with both JENOVA cells and mako (Hojo's notes only say JENOVA cells), but he probably was. So Cloud was given the medicine either shortly beforehand or afterwards, apparently not long enough to properly fend off the JENOVA cells. And who knows if it was even enough to do so in the first place. But what saved Cloud from the same fate as the rest of the Sephiroth clones was Tifa. When he saw Tifa, what was left of his consciousness triggered a reaction with the JENOVA cells to make him into the person that he became. Otherwise, he would have just stayed the way he was and one day wondered off to the north crater like the rest of them. When he falls into the lifestream the first time and receives mako poisoning, he kind of like he was heavily injected with the medicine for JENOVA cells. So when they finally finished working and Tifa helped him find his consciousness again, he was himself again. Notice that from here on through the game he no longer experiences any voices or meetings with himself or headaches of any kind. This is just they way I see things though.