How do people do the Russian transformation dance?

It's mostly in talent shows and suppose to be a brain teaser for the public. If you see shows like America's got talent or Australia's got talent they are capable of changing their outfits or hair under pieces of material or boxes in just a few seconds with the partner holding up the material and shaking it about. They leave no clothes on the floor only the material they change their outfit behind and they change into beautiful outfits in the way of a dance. How do they do it? It's been on my mind for ages and it's got to the point it irratating to try and figure out. They do it so quick there is no chance they are capable of changing there outfit the normal way. Also what's the proper name for it? A dance like this?