They are an interesting specimen, the first ever Escaped Experiment, and the first experiment Fiona ever made.
Fiona created a robotic test subject that she tortured endlessly for "testing" purposes.
The mistreatment was so severe that their data corrupted itself, with only seven sectors of it working properly, but separated from each other, and forming their own personalities and identities.
When they met the Doctor, he helped them by reprogramming the sectors to have different voices and different colored lights, and allowed each of them to give themselves a name, and to explore their identities.
Faulty - Green - They/them
Still trying to figure themself out, especially since discovering that they aren't just one person.
Screw - Purple - They/he/she
The smartest and most social of the seven, but often hard on themself when they get something wrong.
Toy - Yellow - They/he
Basically a child, he is of course childlike, playful, and very innocent, not understanding the bad in the world.
Unknown - Pink - They/she
Unknown is the shyest of the seven, struggling with severe anxiety and is very sensitive emotionally.
Buzz - Orange - She/her
She often acts cold and mean, but it's really because she has trust issues with anyone outside the other six.
Update - Blue - He/him
A soft, calm, caring, and comforting presence, Update is a caretaker of sorts for the other six as well as the other experiments.
Null - White - They/it
A nonverbal, scared sector. Nobody knows what to call them, so they resorted to Null, and they/them pronouns (sometimes it/its). They don't understand anything about the world outside the body, and whenever they accidentally take control, they run and hide immediately, refusing to go near anyone.
Extra tidbits:
Yes, they can "co-control" the body. You can tell because they may have two or more light colors at once, and whoever's talking will have their voice synthesizer used.
They also have a shock ability. If they touch something, they can choose to send an electric shock to it. (Null uncontrollably does this)
