What I'm not sure I understand is when the "switch" occurred. Can he even do that? Is swapping bodies under the realm of his power? Someone explain to me the chain of events if you can...
Aizen's power is absolute hyponosis, while not being fully explain seems to allow him near total control of the senses. So at any time he can make those under its influence see, hear, smell anything.
Sequence of events.
1. People attack Aizen.
2. Sometime during the fight, Aizen creates an illusion of himself to continue the fight, and he flash steps over to Hinamori.
3. Aizen picks up Hinamori and flash steps back into teh fray, setting her up in his place.
4. Aizen flash steps back to where Hinamori used to be and lies down on teh ground.
5. Gin rolls his eyes.
6. Aizen tells Gin to shut up "'cause this will be totally dramatic."
7. Aizen reveals.
During this whole time Ichigo is like "W-T-F mates?" but no one can hear him because Aizen is controlling their senses.