In a future timeline, the earth was visited by a species known as the Slarkovs. Having lost their home planet and in search of a new one, earth was the next habitable planet for them. Humans and Slarkovs made a deal with each other in return for the Slarkovs living on earth. The Slarkovs traded their technology and knowledge for a new home. They were similar to humans except for some of them who had slight differences so fitting into the society wasn’t a problem.