Jonni and her father, Jim Thunder, started the "J. Thunder Detective Agency" in Los Angeles, California years after he was let go from the police force, apparently because he wouldn't take bribes. He died from his own vices or as Jonni describes it "An animal attack ... too many Camels [cigarettes], too much Wild Turkey [whiskey]." Shortly after his funeral, Jonni returned to their office to find a man who been waiting for her but was now deceased. An investigation ensued. conducted by Detective Mike Sanchez and Jonni eventually returned to her office to face off against a robotic bug, which she whacked with a lamp. Though she told the Police of the attack, they would not believe her. Later, she met up with Clarence "Slim" Chance, who was an old friend of her father. He told Jonni the story of a statue her father possessed, which was found in a South American country and given to Jim by a man he himself had put in jail. Chance was willing to pay her $100,000 for the statue. She retrieved the statue from a repair shop where it had ended up because it had been a part of the lamp she used to stop the robot. Taking the statue to the meeting place Chance had specified, Jonni was instead accosted by a man and inadvertently released the energy of the statue, freeing the creature called Thunderbolt!
Jonni apparently had mental control over the Thunderbolt creature, though she herself was rendered unconscious when it was active. Using this newfound power, she eventually thwarted the schemes of both Slim Chance and the deranged exotic dancer Red Nails, both of whom knew of the statues power and intended to use it for their own nefarious ends. Later, Jonni would become involved in the Crisis on Infinite Earths, aiding the Star Spangled Kid against Knodar, the Last Criminal (a villain from the future) and seemingly losing her Thunderbolt power. She also attended a detective's convention around this time. Jonni began a relationship with the Star Spangled Kid (who later became Skyman) and he and his teammates in Infinity, Inc. aided her when the Thunderbolt returned, proving to be a hostile alien entity which had bonded itself to her. The Thunderbolt was imprisoned in the statue once more and Jonni remained an associate of Infinity, Inc. until the death of Skyman.
- Energy Transference: Jonni Thunder has mental control over her Thunderbolt. When she takes control over Thunderbolt, she leaves her body and possess the genie.
- Vulnerability to Unconsciousness: While in possession of Thunderbolt, she leaves her human body unconscious and open to attack.
- Although this character was originally introduced during DC's Earth-Two era of publication, their existence following the events of the 1985–86 limited series Crisis on Infinite Earths remains intact. However, some elements of the character's Pre-Crisis history may have been altered or removed for Post-Crisis New Earth continuity, and no longer apply.
- 21 Appearances of Jonni Thunder (New Earth)
- 4 Images featuring Jonni Thunder (New Earth)
- 1 Quotations by or about Jonni Thunder (New Earth)
- Character Gallery: Jonni Thunder (New Earth)