Plot
After foiling a purse snatcher who steals Jenny Johnson's purse on the subway, Matthew Saunders becomes her "hero" and starts dating her. After several dates, Jenny displays increasingly neurotic and aggressive behavior, becoming more demanding and ultimately injuring Matt and destroying his bed the first time they have sex.
Soon after, Jenny reveals to him that she is in fact the voluptuous blonde superheroine G-Girl, who received the powers of flight, superhuman strength, speed, heightened senses, invulnerability, super breath, and heat vision after being exposed to radiation from a crashed meteorite as a teenager. She becomes more controlling after revealing her powers and Matt is overwhelmed.
Hannah Lewis, Matt's beautiful co-worker, flirts with him, although she is going out with a handsome but shallow underwear model. As their friendship develops further, and after becoming aggravated with Jenny's escalating jealousy, Matt ends their relationship.
An enraged Jenny vows to make Matt regret it. She uses her superpowers to publicly embarrass him, throwing his car into space and eventually causing him to lose his job as an architect by stripping him naked during an important meeting.
Professor Bedlam was formerly Jenny's high school boyfriend, Barry Lambert. While about to become intimate they were interrupted by the crash of the meteor. He saw her obtain superpowers, then watched and became embittered as she ignored him for other guys, something her new charisma made possible. Consequently, he studied to be a supervillain and is now G-Girl's nemesis.
Bedlam contacts Matt to enlist his aid in defeating her. He refuses and makes plans to leave the city. As Matt does, Hannah contacts him. She has broken up with her cheating boyfriend, and after confessing their feelings to each other, they end up sleeping together.
Jenny (as G-Girl) finds them in bed the next day. Enraged and jealous, she attacks them with a great white shark. Fed up, Matt contacts Professor Bedlam; at his house he accidentally sees a room in which he has a shrine showing his secret continuing adoration of Jenny. Matt agrees to help him defeat her, as long as Bedlam retires from being a supervillain.
Matt must lure Jenny to another meteorite that will draw away her powers, leaving her a normal woman. He agrees and meets her for a candlelit dinner at his apartment, under the pretense of wanting to resume their relationship.
Hannah arrives to see Jenny sitting on Matt's lap. The two women fight, and in the struggle, Jenny's superhero identity is revealed to Hannah. Bedlam's trap is sprung, and Jenny's power is absorbed back into the meteorite, incapacitating her.
Professor Bedlam appears, but reveals that he has no intention of keeping his promise to retire from villainy and in fact plans to take the powers for himself. While he and Matt fight, Jenny crawls to the charged meteorite attempting to regain her powers. Hannah intervenes just as Jenny grabs the meteorite, which explodes in a burst of power.
Both Hannah and Jenny are catapulted off the roof, apparently to their deaths; Jenny appears within seconds, powers restored, threatening even more mayhem. Hannah unexpectedly reappears, having also been exposed to the meteorite and gained the same powers as G-Girl. She saves Matt, and the second fight between Hannah and Jenny is a full-on super-brawl, destroying part of the neighboring properties.
Matt ends the fight at a fashion show by revealing to Jenny that Bedlam loves her and making her realize that he is her true love. She is softened and embraces her former nemesis as the spectators cheer.
The next morning, Matt and Hannah meet up with Professor Bedlam (now just "Barry") and Jenny. As cries for help are heard from afar, Jenny and Hannah, now partners in crime-fighting, take off to tackle the emergency. Matt and Barry are left holding their girlfriends' purses and clothes and leave to have a beer together.
