Smiler
Bad Boy Timmy! Zero!
History
The Smilers were mechanical androids that were used as "guards" on Starship UK. They were placed in booths and if at any time a citizen of Starship UK decide to press the protest button, they would switch to their demonic face and come out and attack the protesters. They had three faces that they would present to anyone that approached them and could change there face by turning around. They where capable of killing a human being by getting out there booths and walking. They where destroyed after the Doctor found out the truth about the Starship UK and what they were doing to people. (DW: The Beast Below)
External Links
http://www.sylvestermccoy.com/newdoctorwho/
http://www.bbc.co.uk/doctorwho/dw/characters/Smilers