Awesome animation! Even my wife is sitting here impressed. To stop it on a frame, hit "Stop," and then hit "Reload" to make it re-animate (you won't have to actually re-download the whole thing...)
The cracks change because it is a series of still pictures of different shots instead of a movie. It came from a website of a company offering fast photo equip: http://www.kurzzeit.com/
They have some good stop action shots too.
No pun intended.