I plan to get an iPhone, one of the tricks I can think of is to use it to play a joke on my friends.
This is how the joke goes. I would ask my friend to pose for me in the name of testing the quality of the camera. As I snap his/her photos, instead of showing his/her real face, I want the snapshot to be replaced with a picture of a pig (say), or anything that would elicit laughter.
Is there such an app available?