300x600 ad Takes Over the Screen

TurntableKitchen has a great example of a screen takeover done right. When you hover over the ad, it counts down from 3 and plays music similar to music you would hear while looking into a crystal ball. Once the countdown reaches 1, the screen becomes the ad with a mini interactive microsite. This ad was very interesting and engaging. Two examples are below.

Twix ad:

Colortopia example:
What's interesting about this ad is when users "X" out, there is a "before you go.." survey that comes up.