Smiler

The Smilers were a race of androids that were aboard the Starship UK.

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The Smilers were androids, mounted in booths across Starship UK and used as key instruments of Hawthorne's police state. At any time a citizen broke the law or was deemed unneccessary (even children), the Smilers would take action. The terrified population kept their booths clean and never dared get too close to them. While they initially appeared to be merely in booths, it turned out that in extreme circumstances they could be made to leave the booths and attack. They were, however, vulnerable to handgun fire.

The Smilers rotated their heads to show three faces: happy, angry (for warnings), and malevolent (when attacking). While they had three faces, they appeared to rotate their heads 180 degrees (which could mean they'd only have two). This might mean that faces can be removed when they rotate. It is unknown if the Smilers killed their victims.

They can repair themselves when damaged.

It's unknown what happened to the Smilers after the Eleventh Doctor and Amy Pond revealed and stopped the conspiracy on Starship UK, though the Winders are presumably still around. (DW: The Beast Below)