Penny and Simon are the children who own the toys in The Secret Life of Toys.
They are usually seen in the beginning of each episode, playing with their toys in the playroom. After they leave the room, the toys come to life to have an adventure, usually inspired by the children's games.
Penny and Simon own almost the exact same toys as Jesse and Jamie in The Christmas Toy, including Rugby Tiger, Ditz, Balthazar (a slightly different teddy bear, but with the same name and voice) and Mew, who used to belong to the cat.
The children's games have influence on the world of the toys. When they fight over a toy, it becomes invisible for the other toys until said toy is shared properly. Pretend creatures like lions and monsters become reality for the toys whenever the children say they're there. The toys never refer to the children by name; they just call them "the children", "the little girl" or "the little boy".
Penny and Simon's father (voiced by Jerry Nelson) and mother were seen occasionally as well. Other mentioned relatives include Uncle Charlie and Cousin Donald.
The audience never got to see the children's faces.