I already tried this: if (canSee(Wissenschaftler.class)) { getWorld().addObject(new Kind(), getX(), getY()); getWorld().removeObject(this); } But it doesnt work, when i run the scenario an error appears telling me that "the actor is not in the world" The second problem is, that with this code many children appear instead of one.. I hope you can help me find the right code. :)