And we're back to the body horror! Didn't think we could leave it for long, did you? Of all the aliens that have ever taken over and possessed a human host in Doctor Who's long history, and boy have there been a lot of them, the water creatures from Waters of Mars have to take second prize (first prize is later on this list.) It's scary enough to think that one could lose one's mind, personality, and memories with a single drink of water, or even by being touched by a single drop. But to then have one's face turn into a cracked and ruined mess, spewing water non-stop, and to have one's single purpose be to infect as many others as possible... Yikes. Doctor Who has never really done a proper zombie story, most likely because that would be a bridge too far, but this one comes closer than just about any other. Except Curse of Fenric, maybe. (See, Haemovore fans? We didn't forget you!)