i have theory :P
maybe nagato is bed ridden, and have a way to trasmit the chakra
and ability to the 6 bodies...some far fetched...:)
possible, Nagato controlling 6 bodies in the shadows :)
was re-reading ch425, the chapter makes Shizune and Ibiki look
like idiots when they were shocked that the corpse inside the dead
Animal Realm's mind could also summon. Can't they realise that the
corpse replaced the dead one as the new Animal Realm? In an army,
when a top general gets killed, naturally a new general will
surface, same theory...
The Orochimaru vs Third Hokage fight should also have proven
corpses have the ability to fight also. IMO nothing to be shocked
at lor.
Note: just a random rant, nothing against Naruto manga :)