The old adage 'be careful what you wish for' has the potential to become true in the most unlikely circumstances. What are you willing to give up for money? For power? For fame?
That's what the Andromedans exploited when they found Earth in the year 2000. They offered a small portion of humanity, those they deemed special, an offer they couldn't refuse -- what they wished for in exchange for the human's life.
Many took the offer, while others refused. This unfortunately led to the parasitic creature taking over the person's body and mind, locking what remained of their spirit in the back of their head, watching their body on autopilot. Unable to re-take control of the body.
It was a foolproof plan... At least, until a juvenile Andromedan, outcasted by their society for their inexperience during the invasion, decided to break from the group. When they found the small Carrera family home on Equinox Point, they met a child named Derek.
Instead of exchanging Derek's wish for the young boy's body, the Andromedan had a wish of their own -- to not be lonely. Derek, in his childish way, decided to use this as a way to get a new friend.
With this pact, the Andromedan, now named Castor, had partial control over Derek's body. Acting as an imaginary friend -- who would occasionally take over Derek's body with the boy's permission -- the pair were inseparable. However, Derek had kept Castor a secret from his family...
At least, until 20 years later. When a recent Andromedan invasion results in the death of his parents, Derek comes clean to his older brother about Castor's existence, partially out of fear. While J.D. is hesitant to accept, he eventually comes around, agreeing to help Derek and Castor placate Castor's kind and try to find more like Castor.
