Auton

Autons are plastic mannequins animated by the Nestene Consciousness. They are armed with a concealed weapon in their hand and while they can appear to be obviously plastic, they can also be indistinguishable from the race they are infiltrating.

In Worlds in Time
Autons can be found in the Earth interventions. Since the "Living Plastic" they are made from is malleable, they may initially appear to be Humans or Silurians.

In Doctor Who
Each time the Nestene invaded Earth (twice in the 1970's, and once again in 2005), the Autons were the primary invasion force. The first attempt was shown in the episode Spearhead from Space (1970). Although the Nestene come from the Planet Polymos, they used their telepathic powers to make Humans mass-produce inert plastic Autons for the Nestene to animate.