This instructable will show you how to easily create the illusion of zombies on your house, or anywhere. The hard way of doing this, involve developing a undeadly virus, and infecting your loved ones (not recommended). Check out the video below to see the final product:
I use the term "Projection Mapping" lightly here. There are some amazing examples available online (e.g. http://www.youtube.com/watch?v=gy_jyxoWj5c) and it takes some specialized software and knowledge to accomplish this. More specifically, you need to work out the geometry of all the surfaces you are projecting onto (the more complex the shape, the better the result) and deform your video to fit that geometry. What we are doing here skips all this complexity by using the same vantage point for the filming and the projecting.