Smilers are a race of androids that appear in the British sci-fi series, Doctor Who, primarily in the episode "The Beast Below".
Smilers are displayed within booths and have three distinct faces that convey their state of being - when smiling they are pleased and will not attack, when they show a look of displeasure they are warning people and when they show a face of pure rage they will launch an attack.
Smilers worked for their creator Hawthorne and installed fear in the population of Starship UK by feeding any citizen who broke the law to the Star Whale that acted as the vessel's support - they were also known to attack citizens who were merely deemed "no longer useful".
Smilers did not feed children to the Star Whale however, instead they sentenced minors to work at the Tower Of London - although they tended to stay within their booths when necessary they could leave the booths and become free-roaming.
The population was terrified of these machines and for good reason as they could effortlessly repair themselves form a great deal of damage, such as being shot.