On added to world.

You can write a subclass of Actor say MyActor and define or overwrite an new definition of setLocation. Then you have all your actors become subclass of MyActor (which has the new definition of setLocation. For example inside MyActor you can write this setLocation method public class MyActor extends Actor { public void setLocation(){ super.setLocation(getX()-getX()%50, getY() -getY()%50); } }