Penny is Inspector Gadget's brilliant niece who often helped him in his cases, sometimes against his will. She is played by Michelle Trachtenberg in the first film, and by Caitlin Wachs in the sequel.
Penny is first seen waking up her uncle (who at the time is called John Brown) with Brain who licks him in his sleep from a Police hero dream and reminds him that tomorrow is the day parents come to school to talk about their careers.
She asks about the letter concerning his application to become a full rank Police Officer, she looks at it and he tells her that two years experience isn't enough to be a cop.
Her uncle is concerned that being a security guard isn't the best job because of all the briilant jobs her classmates' parents have and thinks he can do more as a real Police Officer. Penny assures him that she is proud of him no matter what job he has.
After her uncle had an accident involving an encounter with Sandford Scolex, she watched as he was rebuilt by Dr. Brenda Bradford as the first Cyborg Police Inspector for the Riverton Police department: Inspector Gadget. She then helps her uncle get ready for a celebration party of his acceptance. Penny knows that Gadget has an infatuation for Brenda Bradford and tells him to loosen up a bit and be cool when he sees her.
Presumably after being picked up from school the next day, Penny helps Gadget with his case on the murder of Artemus Bradford (Brenda's Father) by noticing a Scolex Industries truck similar to initials "SI" that Gadget found on a small circular piece of metal which makes him realise that Scolex (Now Dr. Claw) was behind the murder.
They drive to Scolex Industries, Gadget goes inside to warn Brenda leaving Penny and Brain in the Gadgetmobile to take them home. When they arrive at Gadget's house, they meet Brenda who has found out that Claw killed her father and find out that something has happened to Inspector and go after him using Gadgetmobile's tracking system.
They find him at a rubbish dump where he had been placed after he was de-activated by Claw. Even though his Neuron Synapse Amplifier chip is gone that was the main source of his functioning body, a tearful Penny says that he has the heart to still function by himself. Suddenly after a kiss from Brenda, Gadget begins to move again much to the joy of his niece and the scientist.
Gadget and Brenda go after Claw and drop Penny and Brain of at home. Penny takes the bus and arrives at Scolex Industries for evidence involving Claw.
Inside she tells Brain to split up and go in different direction, she finds Sykes one of Claw's henchmen trying to flush a cybernetic foot that is evidence in his boss's crime. He aims his gun at her, but she ends up persuading him that a life of crime isn't right for him and gains evidence that Claw made an evil version of her uncle to terrorize Riverton.
Later after Chief Quimby arrives after Gadget defeats Claw to him Gadget for his crimes against the city, Penny arrives with a tearful Sykes who admits everything, much to the astonishment of the now caged Claw. She is given a thumbs up sign by her uncle and she returns it.
She leaves with her uncle (who is now dubbed a hero), Brenda and Brain and heads back home. During the end credits, she is seen testing her latest invention of her communicator watch with Brain who responds in a human voice.
Inspector Gadget 2
Characters: Inspector Gadget | Dr. Claw | Penny | Brain | Gadgetmobile | Brenda Bradford | Artemus Bradford | Chief Quimby | RoboGadget | Robo Brenda | G2 | Sykes | Kramer | Mad Cat | Professor Baxter | Brick | McKibble | Squint | Jungle Bob | The Ninja | Mayor Wilson | Thelma | Guru | Mr. Morgan
Locations: Riverton | Scolex Industries | Police Headquarters
Songs: Inspector Gadget (song)