CKeditor Fake Objects

I'd like to insert a fake object into my editor window (similar to how the Flash plugin works). Behind the scenes it would just create a div that I will parse out later.. something simple like

<div id="123">开发者_如何学Python;</div> 

but would be rendered on the screen with a placeholder image. I've looked around but haven't found any straightforward examples of how to do a substitution like this.