SmilersSmilers are androids that lived in booths upon the Starship UK from the episode The Beast Below (Series 5 : Episode 2). They were a form of law enforcement, and had three faces – happy, displeased (for warning citizens that their actions are not right) and angry (for attacking or enforcing the law fully). The heads would rotate 180 degrees when they were changing faces (indicating that faces could also be removed/replaced, because a 180 degree rotation of the head should only give two faces).
They could also leave their booths to attack, as they did to the Doctor and Amy. The Smilers were responsible for feeding the criminal members of the population, or members that were unnecessary to the Star Whale, except for children which the Star Whale would not eat, and would be sentenced to work in the Tower of London. The population were terrified of the Smilers and kept their booths clean but never daring to get too close if they could avoid it. The Smilers also have the ability to repair themselves if damaged, such as if they are shot, as shown when Liz 10 shot a couple of Smilers, and they repaired themselves.