Scenario
When Aizen joined the Menos in Hueco Mundo not every hollow wanted to follow him. These hollows formed a faction of they're own in an atempt to take down Aizen Sousuke and gain control of Hueco Mundo in his place. They're plan was to combine they're strength into a force which would make copies of the Arrancar army, so that the two armies would fight amongst each other, and the hollow faction rise up in the chaos.
They underestimated the Ex-Gotei 13 captain though. He had already dispatched a force to take them down, the force reached and slaughtered them, but not before they set off they're device.
Without the Hollow Faction there to control it the effect of the machine didnt stop when it was supposed to and lasted too long.
A ripple has crossed the three worlds. When the "Reflections" made by this ripple were born from people's hearts and souls they were not exact doubles.
Good Reflected Evil.
Evil Reflected Good.
The Arrancar are bemused when suddenly Arrancar with they're hated human personalities appear.
Whereas the Shinigami and the Humans are concerned when duplicates with what can only be described as incarnations of they're would-be hollows appear.
It's a new chapter in Bleach and everyone's inner demons, or angels, have been released into the war.