*Penny is Inspector Gadget's niece and one of the main protagonists of the franchise. Penny secretly helps out her Uncle Gadget with his missions and does all the work, but she lets him get all the credit in the end.

Penny now joins Gadget on his missions and is an agent in training. Despite being Gadget's new assistant, and that Gadget is now aware of Penny's capabilities, he still doesn't pay attention to her and does what he wants instead. Penny is fourteen in this, it takes place after Gadgetinis and before Caper.

Penny is precocious, intelligent, brave, cute, tomboyish, resourceful, and anonymously solves the cases for her Uncle Gadget, something which he is totally oblivious to. Penny also loves her uncle very much and looks up to him. While it is not stated if she and/or Gadget have any other family members in the TV series, movies, or spin-offs, Gadget seems to be the only family she has got, and "Gadget and Old Lace" and a few episodes of Gadget and the Gadgetinis, including "No Brainer", confirm her to be an orphan. Penny foils Dr. Claw's plans, leaving Gadget to get all of the credit for doing so, even though he didn't do anything at all. This makes sense because Penny would be in serious danger if she got the credit.

Penny often stares around M.A.D.'s hideout or setup location to find out what they are up to; however, she usually ends up getting caught by Claw's henchmen and she either escapes by herself or calls her loyal pet dog Brain to rescue her. But when she and Brain are both captured, Gadget becomes exceptionally useful and competent and goes out to rescue both of them. Gadget loves Penny more than anything and he sees acting like a pretty girl. Penny is also very knowledgeable; for example, in "Clear Case", when she and Brain are in a laboratory of a diamond mine in South Africa, she knows how M.A.D agents are making invisibility suits to scare off miners by making them think they are ghosts. Quoting: "Diamonds refract light. They discovered a way to grind them into a powder and make a diamond cloth. It's like a coat made of mirrors: It deflects light so you can't see it."

Penny is also very patient and progressive, particularly when putting up with her uncle's clumsiness and stupidity.

In the 2015 series, she is now a junior agent. She is a lot more active and is a good fighter. She acts like a typical teenage girl when she's not on duty. She is very intelligent in addition to her cuteness and beauty and is capable of hacking into almost any computer-based system. Despite being fearless and a genius, Penny does have her weaknesses. It is shown in episodes such as "Claw's Nephew", "Gadget 2.0", and "Eye of the Dragon" that she has a strong weakness for boys and gets nervous when they're near her. She might be in love with Dr. Claw's nephews, Billy Thaw and Talon.

Penny has shoulder-length blonde hair styled in pigtails. 3 years later, she is 15 in the 2015 series.

In the 2015 series, she wears a red and white hoodie, blue jeans, red boots with white laces, and red fingerless gloves. On two occasions, she is seen wearing a similar uniform, except it is black with neon blue stripes along the seams, and the boots have neon blue laces, as shown below. Penny's swimwear is also different, as it now consists of a colored tank top and beach shorts after her original outfit (and resembles her swimwear from the last page of the 1984 Golden Book Inspector Gadget in Africa). Her sleepwear in this series is also modeled after her original outfit.*