The above Flash movie is embedded in Internet Explorer using ActiveX via the object element. When you mouseover the Flash movie you should see that it's already activated.
If you view source (right-click » View Source) for this page, though, you'll see that the HTML is in the page. Yet, the ActiveX object does not need user activation!
The external JavaScript file that makes this possible parses the page, finds the object element, and using DOM magic, clones it, deletes it, and re-writes the HTML using the cloned node, which counts as using an external script to activate the object element.