Originally posted by: Vegechan
First and foremost, I thought the Manga shots were pretty clear, Urahara put the Hollow/Shinigami orb in Rukia before the gigia was even in question. Why did he choose her? I doubt Aizen would know that, and only Urahara does. In due time I'm sure we'll learn why he chose her.
Secondly, we need to look back at the oringal transfer of Rukia's power to Ichigo. We all assumed that Ichigo's natural spirit ability (which still is unexplained as to why he had such power. I'm guessing someone in his family has a history of it. I'm going to guess his mother because his father seems absolutely clueless to the spirit world.) was way he was so strong as a temporary Shinigami, and why he took all of Rukia's power when she only inteded on giving him a small portion of it. But what if, her transfering the power over was how the orb makes someone a hybrid hollow/shinigami?
Aizen talked about the incredible strength gained by this hybrid form. Right from the start, with his giant sword, Ichigo was powerful. So powerful resitsu leaked out of him, giving the ones closest to him, Inoue and Chad, powers of their own (I believe that's how Urahara explained it.) So powerful, that he scared that uber hollow. The only problem with this insane amount of power, was that he can't control it.
Now, I also want to bring your attention to a few other things. Hollow Ichigo has only intervined when Ichigo was about to die, which in turn. kill him. He took over in the Byakuya fight, had the mask stop a critical hit, and one other important time (at least by my theory.)
I believe, Ichigo, from the moment Rukia transfered her powers to him, was a shinigami/hallow hybrid. I don't think the orb transfered to him, but I believe the act of transfering the powers activated it and did it's thing. I also think Urahara knew this. When he threw Ichigo into the pit, I don't think Ichigo himself could have gotten out by himself. The reason Ichigo had the mask one and looked like a hallow? Because before Ichigo died, the Hallow came out, just like in the Byakuya fight, and made Ichigo escape, saving Ichigo, and himself.