How to enqueue a modified version of Thickbox?

I’ve my plugins using the wp_enqueue_script and wp_enqueue_style. However, I’ve modified the default Thickbox script by adding some transitions and fades and I would like to enqueue my own instead of the default WordPress script. Maybe it’s possible to redefine the javascript function… the easiest way would be renaming thickbox.js to fancythickbox.js and adding a suffix to “tb_” but I would like to preserve integrity of the loaded scripts.