Penny is a kind, lovable, and intelligent 13-year-old girl. Ever since she was little she loved Bolt dearly and was heartbroken when she found out he ran away. She clearly isn't fond of her agent who rarely listens to her and tries to persuade her into doing what he wants. She is also very loving towards all animals, including Mittens and Rhino, whom she presumably found at the hospital and adopted.
Penny is a slender, pre teen girl with fair skin, short auburn hair, and brown eyes. She wears a red T-shirt over a chocolate long sleeved shirt, gray jean shorts, gray and white striped tights, along with brown socks with a red line and brown boots, in which she mostly wears when she's acting in the Bolt TV Show. When not acting or doing rehearsal, she wears casual outfits such as a dark blue long sleeved T-shirt, brown pants, and black shoes. After quitting the TV show and moving on to a new life with her pets, she wore a light green T-shirt, blue jeaned shorts and grey shoes.
When first adopting Bolt as a child, she wore a yellow T-shirt with pink lining and purple flowers, blue shorts, and pink shoes.
In the video game adaptation of the film (which mostly focuses on the fictional TV show), one of her outfits is a spy outfit which consists of a black helmet with night vision goggles, a black T-shirt with red lining over a black long sleeved shirt, black pants, a holster, and grey shoes; in which she uses when spying on a mansion owned by Calico. In later levels, however, she wears her iconic outfit from the film, though she also wears a grey scarf over her red T-shirt and white pants (during cold weather), and green shoes, as well as a red tanktop.
Penny was 8 when she adopted Bolt in the Silverlake Animal Rescue, who lived with the puppies of the shelter and his favourite toy Mr. Carrot. Five years later, she and Bolt became the stars of the hit TV show Bolt, where they foiled the evil plots of the nefarious Dr. Calico. However, Bolt believed everything that he saw to be real, and that he had superpowers, Bolt was assigned the task of protecting Penny from Calico’s henchmen. In one of the episodes, she and Bolt are in a large city, where they are spying on Calico. After interrogating one of his thugs and learning of his location in Bolivia, Penny was pursued on her fold-up scooter by Calico's helicopters and motorcycles. One of the men tried to lead Bolt away by deploying a disc-shaped bomb on the back of a gas tanker, but Bolt swiftly dispatched the bomb and reunited with his person. Then, Bolt used his super bark on the forces that surrounded the airport. Having accomplished their mission, Penny poses for a Polaroid picture with Bolt before carrying him through the debris of "super barked" cars and "unconscious" evil henchmen into their set trailer. Penny adds the newest picture to her wall of countless pictures of her and Bolt before trying to play with Bolt, who is convinced the henchmen will come back for Penny and is determined to protect her. Sadly, Penny hugs Bolt goodbye for the weekend and leaves him in his trailer.
Saddened about having to leave Bolt alone again, Penny pleads to her agent to take Bolt home for the weekend, but the agent simply tells her to "put a pin in it." She is then later taken by the rest of the staff to be on a cover shoot while Bolt gets bullied by one of Calico's feline henchmen. The next day, Penny and her dog Bolt "infiltrate" Calico's secret lair in Bolivia, where they try to get information to where her father is. However, Calico appears and begins to "kidnap" Penny, resulting Bolt being taken back to his trailer after the shooting ends. As a result, Bolt escapes and Penny tries to get him back by sending out lost dog flyers. However, Mindy Parker from the network reminds her that they have to keep in production, or else good people will start losing their jobs.
After undergoing a cross country journey back to Hollywood from New York, Bolt reaches the studio, finding Penny embracing his lookalike. Unaware that Penny still misses him and that her affection for the lookalike was only a part of a rehearsal for the show, he leaves, broken-hearted. Mittens, on a gantry in the studio, sees what Bolt does not - Penny telling her mother how much she misses Bolt. Realizing that Penny truly does love Bolt, Mittens follows Bolt and explains. At the same time, during a shooting of an episode, Penny is being held "captive" by Dr. Calico until the Bolt-lookalike arrives to "rescue" her, along with her father. However, the Bolt-lookalike panics during filming and accidentally knocks over torches, setting the sound stage on fire and trapping Penny. Bolt arrives and reunites with Penny inside the burning studio, being rescued by firefighters as they succumb to smoke asphyxiation.
Penny and her mother subsequently quit the show when their agent attempts to exploit the incident for publicity purposes. The show continues with a new actress replacing her and also with a new alien abduction storyline, while Penny herself adopts Mittens and Rhino, and moves to a rural home to enjoy a simpler, happy lifestyle with Bolt and her new pets. After watching the said episode, Penny takes a selfie with her new pets and begins to play outside with them, enjoying their new life outside Hollywood.
Penny also appears in the short, but with a small role. Here, she and her dog Bolt have been captured by Dr. Calico and are about to be dipped in a pool of lava, inside a giant warehouse impenetrable to both people and dogs. Unknown to them, Penny's father has been witnessing the events through Bolt's collar, prompting the scientist to infuse Rhino with Bolt's powers and send him to rescue them.
When Rhino destroys most of Calico's defenses using laser vision while riding a missile like a surfboard, she and Bolt witnesses him and are about to be rescued. However, as the missile hits the tight rope about to dip them in lava, Rhino jumps off the missile and saves them in the nick of time. She then congratulates Rhino for saving them before the latter tells her that he has an "urgent matter" to attend, which turns out to be a concert in which Rhino sings The Best of Both Worlds. After Rhino realizes that his adventures was just a dream, Penny is later shown sleeping in bed.
- Penny is only referred to as such on the TV show (and by Bolt and the animals), meaning that her real name outside the show is unknown. Her mother calls her by her endearments and her agent calls her "My Little Superstar." This led many people to insist they keep Penny as her real name.
- Chloë Grace Moretz was the first choice to voice Penny and apparently recorded all of the character's lines. However, she was quickly replaced by Miley Cyrus, who re-recorded a majority of Penny's lines. Moretz's voice works as young Penny is still in the film, though. Penny's double is also voiced by Chloe Grace Moretz.
- The new Penny featured in the end of the film is somewhat different from the original. Upon having plastic surgery, her auburn hair is much darker and has green eyes.
- Penny is named after the character from the Inspector Gadget series.
- Penny is also similar to Kim Possible from the series of the same name. They both are action girls who have orange hair and try to save the world from evil doctors bent on world domination. The only exception is that Penny is an actress while Kim Possible is not.