In The Worlds End, the 5 main characters' town gets taken over by aliens who convert the inhabitants into what they call "blanks". Later on, after reaching the last pub they find themselves talking to the entity who is apparently the "head alien", who tells them that they invaded the world to provide a better life for everyone etc.
The question is, who was this first alien that came to Earth who then turned everyone else into the "blanks" - it had to start from one in order to propagate to everyone else?