whenever he uses a summoning jutsu he transports the other bodies accross space and time
examples are when he fights against jiriyah and when he enters konohas barrier as 1 person and summons the other bodies. that is what is described as a summoning, it transports the stuff accross from space and time, which is exactly the same thing that naruto does when he summons gama, the only difference is that gama is uber big. also this is also shown that pain can summon bodies and animals and stufff from across space and time is when he summons the centipede in konoha and when he summoned all those monsters when he fought jiriyah
Hmm, true, true, I suppose your right, IN THEORY.
We still haven't seen ANYONE come back from getting sent to another dimension.
I mean, if it was that simple as to just summon someone back, then why was Diadara so scared of getting hit with Kakashi's MS?
And another thing, Kakashi's MS doesn't simply send things to another dimension, he folds them into one single point [Much like a black hole] and THEN it goes to another dimension.
So no, if Kakashi were to send someone into another dimension, Animal realm could not bring them back.
Gotta come back for that one?