My guess is with out the data is that your action has an action object of the character in it too, or you've turned on Onion Skin, under Tools,Options,OnionSkin.
My guess is that you have done something you didn't mean to do it a smartskin.
make an new action and rotate each bone one at a time with the rotate manipulator to see which bone is causing the problem. Then look in that smartskin relationship to make sure there are not bones or poses being animated in that smartskin that you don't want.
This often happens when people forget to turn off the define relationship button when they adjust their constraints poses to make it more simple to be able to rotate the smartskin bone.
Send the model to support@hash.com if you are unable to figure it out, and we'll be glad to take a look at it.
Looks cool, one thing that might help is to assign some of the shirt control points to the thighs on the front character. It might take some smart skin but you might be lucky and have it look good with out smart skin.
Have fun