multiple exposures
Multiple exposures are a really fun thing to do in photo shop, as long as you know how to do them that is. You can create all sorts of cool and funny effects.
first you will need to open two or more pictures. next you have to drag one to the other and make it a new layer. next you will need to add a layer mask and select the brush to the opposite color of the mask. and wherever you brush the layer beneath it will show.
then you get to make funny and weird pictures like this.