I may be confusing myself, but I'm trying to pull off the "Ghost" effect where there's a non-corporeal being who can have people/objects pass through him. I know this can be achieved with green screen (shoot background plate, "ghost" character in front of screen, then people passing through him walking towards the camera separately), but then I think of how to put it all together properly in the editing room and it doesn't make sense (how to get the people walking towards the camera to go from appearing behind "ghost" to passing through to and appearing in front of him).
Kind of like that. Specifically, in one instance there's three characters, two of them are "actually" there, one of them is just appearing there (a la "A Christmas Carol") experiencing the scene as it played out earlier. He happens to be standing in between two people fighting, one thrusts his sword "through" the visiting party and into his opponent.