Creating a MovieClip dynamically is a task you will find yourself doing often in ActionScript 3.0. If you’ve ever tried this is AS2, it required the population of many parameters and a frequent trip to the Flash Help panel. AS3 introduces much simplified solution to dynamically creating a MovieClip.
Dynamic MovieClip Creation in AS2
var container:MovieClip = this.createEmptyMovieClip("container", this.getNextHighestDepth());
Dynamic MovieClip Creation in AS3
var container:MovieClip = new MovieClip(); addChild(container);
Simplicity of this AS3 integration makes for less headaches and cleaner ActionScript code. The key difference is that you no longer have to define a level for the MovieClip to reside on as it is handled by display list.
Hope this helps!