Originally he lunged at the train and took a swipe at it with his right arm. Imagineering bragged that the AA used the force of a 747. Well, that force cause the concrete foundation to literally crumble. They then put the scene into "B-Mode", which is a stationary Yeti with a strobe effect to appear as if he is moving, but he is not. Thus he was dubbed, "Disco Yeti". There is even now a web site commemorating TDO's "EPIC FAIL".
http://www.discoyeti.com
Copycat!!