Silurians

Reptilian civilisation (Homo Reptilia) that used to roam the Earth and escaped below ground when it became uninhabitable. Accidentally awoken by humans drilling deep down, the Silurians have since occasionally butted heads with mankind for dominance over the planet.
Snoring Silurians, unauthorised Earth ambassadors and the (temporary) deletion of Rory Williams
The Doctor toys with a kid’s life and the Silurians return to our screens only to be beaten by a meals-on-wheels van.
U.N.I.T. can’t decide whether to battle Global Warming, a flesh-eating virus, nuclear holocaust, dinosaurs or planet-usurping man-geckos.