Your eyes might tell you differently, your brain might make you believe something else and that gut of yours will say you're right but you're not. There is only one person in this video. You will only see one woman's face. It may look like a different person, but it's not. The magic is in the lighting. Simple lighting changes can change a person's face so much that they look like different people.
Digg found this video on FunComedyLaugh and it shows how important lighting is in taking a picture. Hell, it's probably more important to a picture than the camera taking the picture. A person could look normal, beautiful, evil, grotesque, depressed, jovial and so much more with just little tweaks.