The Apalapucians were the inhabitants of Apalapucia.
The Apalapucians looked somewhat similar to humans. They had a binary vascular system, leaving them susceptible to the disease Chen-7. There were other biological differences from humans; though Apalapucian anaesthetics would work on humans, some of their other medicines could be fatal. (TV: The Girl Who Waited)
The Apalapucians were cultural scavengers, known for their habit of taking ideas from other species. The Two Streams facility was filled with alien artwork and even copies of entire locations. (TV: The Girl Who Waited)
The Apalapucians built the Two Streams kindness facility. It used temporal technology to selectively manipulate the flow of time, allowing patients to live out years in a day. Each patient was kept in a different time stream; they could occupy the same space and never encounter each other. The Two Streams facility also had technology like teleporters for transportation, an interface to help the patients and Handbots for aid. These would not work within a given timestream. (TV: The Girl Who Waited)
The Apalapucians suffered an outbreak of the Chen-7 plague, which would kill in a day. They created the Two Streams facility so that the infected would be kept quarantined but could still have long lives. When the Eleventh Doctor, Rory Williams and Amy Pond came to Apalapucia, they landed in the Two Streams facility and Amy was accidentally trapped there for thirty-six years. They were able to reverse the timeline and save her at a point before that timestream had occurred. (TV: The Girl Who Waited)