Subliminal Talk

I know there some seriously intelligent people on this forum and I was wondering if anyone could explain how this works? I'm baffled! Thanks!

http://www.youtube.com/watch?v=7v-vQHxD-6U

Twins?

It doesn't actually work, the video itself is using an illusion to trick us. It could be video editing with the girl being in on it or it could be as tinygargoyle said, twins, etc...