Slitheen

The Slitheen are a fictional family of massive, bipedal extraterrestrials from the British science fiction television series Doctor Who. They are adversaries of the Ninth Doctor and later Sarah Jane Smith. The Slitheen are a family of egg-laying calcium-based aliens from the fictional planet Raxacoricofallapatorius. Though their family name is Slitheen, their species are named Raxacoricofallapatorians. The Slitheen are instinctive hunters who are trained from a young age to be ruthless criminals whose main motivation is profit. They were convicted on their home world, not willing to return to their planet in fear of receiving a death sentence.

The Slitheen first appeared in the 2005 series episodes "Aliens of London" and "World War Three", and subsequently recur in later episodes of both Doctor Who and the spin-off series The Sarah Jane Adventures.