Sky Smith was created by Miss Myers, a member of a Fleshkind race, as a weapon intended to exterminate the Metalkind. She was later adopted by Sarah Jane Smith. She shared a similarity with Sarah Jane's son Luke Smith in that while she had the physical appearance of a pre-teen, she was actually a "newborn."
Biography
Creation
The Fleshkind and Metalkind had been at war for centuries before "Sky" was born. Sky was created in 2011 by Miss Myers (essentially her mother) as a superweapon that could destroy every single Metalkind across the entire Universe. She had to be primed to detonate which involved her being in vicinity of at least one Metalkind, she would then explode, inevitably ending her life.
Meeting Sarah Jane
Before this could happen however, she was taken by the Shopkeeper and Captain and dropped of at Sarah Jane's house where the Shopkeeper believed she would be safest. She began to blow out all of the electricity in Bannerman Road and Sarah Jane named her Sky because it seemed like she had "fallen out of it". She was primed when she was in vicinity of a Metalkind, she became a pre-teen. She decided that she had to fulfil her destiny to wipe out the Metalkind before Miss Myers could summon them to Earth and slaughter the blue planet. Luckily however, Clyde Langer and Rani Chandra prevented the Metalkind from appearing and the lone Metalkind teleported himself and Miss Myers away from Earth back to the war.
Part of the Gang
Sky met the Shopkeeper again in Sarah Jane's attic who confirmed it was him who dropped her off at Sarah Jane's, Sky wanted to stay with Sarah Jane and the Shopkeeper agreed and then with the Captain teleported away, "Sky Smith" had become Sarah Jane's daughter. (SJA: Sky)
Less than a month later, Sky was enrolled in Park Vale Comprehensive School while she and Sarah Jane were being interviewed by Haresh Chandra it began to rain fish. Sky was the only person who did not fall victim to the curse put on Clyde by Hetocumtek. She confronted Sarah Jane, Rani and Carla Langer and deduced that Hetocumtek was using Clyde's name to escape from his totem pole. She urged Sarah jane and Rani to break the curse on themselves by saying Clyde's name and remembering what he meant to them. They found Clyde and took him back to Bannerman Road where Mr Smith teleported the totem pole into into the attic. Clyde defeated Hetocumtek by shouting his name at the totem pole, the curse was lifted and the totem pole destroyed. (SJA: The Curse of Clyde Langer)
Personality
Upon her transformation or "priming", Sky was very similar to Sarah Jane's first adoptive child, Luke. She knew nothing of the world, a similarity Rani noted early on. Because of her naïvete she asked many questions; wanting to know more about Earth, which she loved. (SJA: Sky, The Curse of Clyde Langer)
She enjoyed Clyde's jokes more than Sarah Jane and Rani and was was very joyful. However she was quite defiant and very brave, ignoring the Bannerman Road gang's protests and was willing to die in order to save Earth and specifically, to save Sarah Jane with whom she had quickly developed a bond. (SJA: Sky, The Curse of Clyde Langer)
Abilities
Sky was created as a bomb to wipe the entire Metalkind species from existence. Miss Myers compared the girl's power to the fury of a supernova. Sky could make electrical devices activate, malfunction or explode by laughing or crying. She exuded an orange aura and could shoot powerful electrical pulses from her hands. These powers were apparently nullified after she absorbed the energy of a power station, though some of her influence over electrical devices remained, albeit more controlled. (SJA: Sky) She was immune to the effects of the curse placed on Clyde Langer. (SJA: The Curse of Clyde Langer)