This is a short tutorial that demonstrates the problems you can have with rotated child objects that are parented to a toplevel object that has non-uniform scaling applied. That is to say that the top level object has been scaled differently in X vs Y. This usually occurs when someone brings in an object, say a character, and after creating the complete parent/child structure they decide they need to scale the top level structure in a non uniform method. This creates a distortion that is applied to all child level objects when they are rotated. There is a simple fix for this issue using a null object. This is demonstrated in this tutorial.