The trick, as far as it is one, seems to be the idea of using simple concepts, emotional and vulnerable moments that we all feel from time to time, and to ground the story there. This gives people a place of understanding to hold on to when the rest of the movie, involving body swapping and serial killers, might take the story to places people don’t understand. The trick itself isn’t necessarily anything most filmmakers don’t understand. However, knowing what to do, and actually making it all work are two very different things. Christopher Landon appears to have a very solid grasp on how to make it work.
