The Slitheen are a criminal family of Raxacoricofallapatorians from the planet raxacoricofallapatorius. They are spread out over dozens of planets and are always trying to make a profit.

In 2006, the Slitheen infiltrated the British government in an attempt to reduce the Earth to molten slag and sell it piece by piece. The family was destroyed by a missle that hit 10 Downing Street. (Doctor Who: Aliens of London/World War Three)

Other members of the Slitheen tried to exact their revenge by stealing the energy of the sun and turning the Earth into a ball of ice. They would sell the energy to buy a fleet of battlecruisers and return to Raxacoricofallapatorius to destroy several rival families. Their plan failed when their energy storage overloaded and exploded. (The Sarah Jane Adventures: Revenge of the Slitheen)