When it comes to ghost photos, they are very easy to make. Just for fun I've made quite a few actually.
This is not the best image, as it for some reason looks very dark, but it was the only I have online.
That guy on the left, rather transparrent, isn't he?
Easy to make: I had two people standing prefectly still and set the shutter for 8 sec. After 4 sec, the guy on the left quickly pulled out of the pic, and for the remaining 4 sec, there is only one person in the shot. Result, a ghost like person on the right.
Oldest trick in the book.
"If guns don't kill people, people kill people - does that mean toasters don't toast toast, toast toast toast?"