Escape to Witch Mountain
Since they had no parents, they were placed in an orphanage with a Starcase as their only item. After seeing Snow White and the Seven Dwarves, Tia predicted that a car was going to hit Deranian and warned that guy not to get into the car that he was going in for a tow truck was going to hit that car. And after that scene, Deranian informed his employer Aristotle Bolt. So Bolt had Deranian be Tony and Tia's uncle. But they escaped and hid in a winnebago owned by a traveling widower named Jason O'Day, and he agreed to take them to where they are going, Witch Mountain, when they got there they finally met their real Uncle Bene. He explained when their home planet was dying they had to come to Earth, Tony, Tia, and Uncle Bene escaped in their spaceship.
Return from Witch Mountain
Now older, they came back from Witch Mountain to take a vacation in Los Angeles. Tony was discovered by Dr. Gannon and Letha and kidnapped him for their dastardly deeds, kinda like Bolt, but luckily, Tia saved him with the help of a group of would-be tough kids called the Earthquake Gang and a hapless truant officer named Mr. Yokomoto, which the Earthquake gang nicknamed Yo-Yo.
Beyond Witch Mountain
Tia and Tony follow their Uncle Bene to Earth in his attempts to find his long-lost-grandson. Bolt discovers that Tia and Tony have returned and he sends out Deranian to catch Jason O’ Day so he can lead Bolt and Deranian to Tia and Tony. Uncle Bene is telling the kids that they must go back to their planet while he searches for his grandson. His grandson was on a nature walk with his class when a bridge broke and Gregory, Uncle Bene’s grandson, moved a big log over to his class with his powers so they could grasp it and they could climb up to safety. Tia and Tony refuse to leave and Uncle Bene dies because of his old age and he lets them search for his grandson. Tia and Tony go to Jason O’ Day, who agrees to help them find Gregory. When they stop to buy Tia and Tony some clothes, Jason goes back to his car and he’s kidnapped by Deranian and Bolt. They give him a drink that makes him drunk and Jason tells them where the kids are. The kids come to Bolt’s mansion to rescue Jason and they run away to a hospital where Gregory is. They tell Gregory all about himself and while they are taking him back home, Tia and Tony decide to stay and, with Jason, find all the survivors and send them back home.
Powers and Abilities
Being brother and sister, Tony and Tia are capable of communicating with each other telepathically and sense whenever the other is in trouble. They each have individual abilities of their own.
Tony can telekinetically move and control inanimate objects using his telekinesis combined with music. His harmonica is shown to strengthen it; though at one point, managed to hover telekinetically and move a baseball bat and mitt without the use of his harmonica and in the second movie he doesn't need his harmonica to use his telekinesis. He also has the minor precognitive ability to see future events. He can also levitate of the ground as seen in the second movie when he levitated to get over the fence. His psionic powers are not as strong as those of his sister's. The other main difference between their psionic abilities is he sees into the future while Tia sees the past and present.
Tia shows some telekinetic abilities in the first movie when she lifts Tony to catch a baseball, but they have greatly improved by the second movie to the point where she was able to keep a literal ton of metal from falling on and crushing her.
She can telepathically speak to and control animals, and has unclear, clairvoyant visions about her and Tony's muddled childhood. She can also render locks useless. The main difference between their psionic abilities is she sees into the past and present while Tony can see and draw places he and his sister will be at in the future. He also has an unusual knowledge of a person's history and knows the places he or she has been before.