Unparalleled in a series since is the diversity of the aliens and monsters present in series one. While we did see the Autons and of course the infamous Daleks return from the original series, there was a rotating cast of original monsters and aliens to complement them. Series one is the reason many Whovians get jittery learning about World War Two, air raids and in particular gas masks - the monsters in the double episode The Empty Child/The Doctor Dances were truly eerie. It seems that putting a small child in a gas mask and having them chillingly plea, are you my mummy? is enough to make any of us dive behind the couch. The Unquiet Dead brought us the gaseous ghostly Gelth from the Dickensian era, The Long Game brought us the giant slug-like (but certainly not benevolent) Jagrafess, and Fathers Day brought us the pterodactyl-esque Reapers, who came to sterilise the world when there was a disturbance in time. With such original monsters and aliens, its quite a shame that many never showed up again after series one!