Here is a relatively easy way to to take a photo of yourself or someone else and make it look like two faces in one. I always loved the candlestick illusion. This is my version of it.
Link to candlestick if you haven't seen it before. http://www.blogcdn.com/www.switched.com/media/2008/09/facevase.jpg
Photoshop or some photo editing software.
A front and side view photo of target.
It takes about 20 to 45 min to make.