Organic animation help

If any of you remember Organic Template Demo on Flashden back in the day (the old swf is attached here), I have a question about the kind of animation that’s in it.

When the preloader animates in, and then the Home page background/box animates in as well… these shapes come in a very cool, organic and bouncy type of way. Is this kind of animation simply a shape tween done very smoothly, or can you do this kind of animation with AS3 and a tweening engine?

I’m trying to see how I can build a basic animation like that… from a single line, bouncing all the way up to a square/rectangle. Any example tutorials out there showing this ? Smooth and elastic like that.

Thanks