Four children pull on the same stuffed toy at the same time , yet there is no net force on the toy. how is this possible?

There was no net force on the stuffed toy, because the kids might have the same strength,  The same force is on both sides of it.  They cancel each other out. They exert a force on the stuffed toy equal in strength but opposite in direction. The forces are balanced and the stuffed toy does not move.  Its like a game of tug-o-war, but you and I have the same strength. the rope would be still and not moving. 

That would be kinetic energy