Despite being the granddaughter of Barry Allen, the Silver Age Flash, and the daughter of one of the Tornado Twins, Jenni Ognats did not at first display any signs of super-speed and grew up a normal child - unlike her cousin Bart Allen (Impulse), who had super-speed from birth, and rapidly aged until his grandmother took him to the 20th century, where Wally West, the third Flash, managed to arrest his aging.
When she was two years old, she was briefly captured by President Thawne, Impulse's grandfather, when Impulse's mother Meloni Allen (née Thawne) brought him back from the 20th century and they waged a campaign against him. In return for her release and the President's promise never to interfere in Jenni's life again, Meloni agreed to return Bart to the 20th century and reconcile with her father.
However, the Dominators, knowing her family heritage, captured her, and the sight of seeing her father tortured activated her latent super-speed, and she managed to escape with her father before stray fire from the Dominators caused their base to explode.
After this, she checked herself into a laboratory to help her learn to co-ordinate herself at super-speed. Once she had learned control, however, she was drafted into the Legion of Super-Heroes. Initially scared and nervous, she almost ran away during her first battle, against the insectoid Tangleweb. Although she convinced herself to return, her running hadn't gone unnoticed by Cosmic Boy. In shame, Jenni thought about leaving the Legion due to her cowardice and so as not to leave her father alone in case she was killed, but Cosmic Boy confronted her, encouraging her to stay and prove herself. Later, at Kid Quantum's funeral, saboteurs planted a bomb and activated the deceased Legionnaire's stasis belt, freezing everyone else and slowing XS down. Jenni managed to save everyone with much effort, and was in turn saved by Cosmic Boy from falling debris. This event strengthened her resolve to remain with the team, and Cosmic Boy congratulating he at the end with the words "something tells me you're going to be a great Legionnaire" was later thought by her to be her "proudest moment" - a happy memory she would focus on in moments of panic - and helped her develop a crush on him.
XS would play a key role in the Legion, distracting the Composite Man by running away with Chameleon while the others worked on a way to stop him; single-handedly saving hundreds of civilians from a tidal wave created by one of the rogue Daxamites during the White Triangle crisis and helping save Dirk Morgna from Doctor Regulus.
XS was one of the Legionnaires who travelled to the 20th century to find a way to save Valor from the stasis zone, but her super-speed caused her to get lost in the timestream. She was found by the 20th century villain Chronos and his "assistant" Lori Morning. Chronos found out that she was from the 30th century, and plotted to steal the time machine she had used to enter the timestream, as his Neron-granted inherent power to time travel caused him to age every time he used it, forcing him to transfer the excess "chronal energy" to others like Lori Morning. With Lori's help, XS defeated Chronos in the present and freed his captives, but another Chronos reappeared, took Lori and went to the 30th century where he was defatted by the Legionnaires there.
XS would then go on to find her cousin Bart Allen, who had been brought to the 20th century to save him from the rapid aging his powers caused. With Bart's and Wally West's (the current Flash) help, XS was able to re-enter the timestream. She was shunted to a future time by accident, where she helped some heroes rebel against a tyrant, inspiring them to form their own Legion. She also encountered her grandfather, Barry Allen (the second Flash), and met the Time Trapper briefly. The Trapper admitted that s/he had been responsible for XS' journey through time and that her ultimate role had yet to be unveiled; he then erased Jenni's memory of their meeting and returned her to the 30th century.
XS arrived just in time to be recruited by Live Wire for his Legion "Rescue Squad". Jenni and the squad arrived just in time to save the other Legionnaires from the Fatal Five on Takron-Galtos, and they were able to force the Five to retreat. Jenni then joined the squad that pursued the Five to Drak IV, where they emerged victorious. After this event, R.J. Brande was drafted as President of the United Planets, and the Legion finally became free to decide their own destiny.
Unfortunately, this wouldn't last long. XS was part of the team sent to Gallan to stop Doctor Regulus. During the battle, Jenni's "heart's desire" was granted when Cosmic Boy kissed her passionately; but unbeknownst to her, the Emerald Eye was causing him to think Jenni was Saturn Girl. And when Leviathan fell in battle, the Emerald Eye which had possessed Violet also possessed Jenni and the rest of the Legion. This possession ended only when the satellite the Legionnaires were on exploded, sending nine Legionnaires and allies through time.
After the remaining Legionnaires managed to get back to Earth, Jenni tried in vain to use her speed to break the time barrier and retrieve her teammates, stopping only when Star Boy increased her weight to the point where she could no longer move.
A little while after, Legion ally Rond Vidar used Lori Morning's excess chronal energy to speak to the Legionnaires in the 20th century. Jenni was crushed when she saw Cosmic Boy and Saturn Girl had seemingly started a relationship. Around this time, started developing close friendships with Kinetix and Lori Morning, along with a crush on M'Onel.
Jenni would continue to be an important part of the team, especially during the Mordru battle, where she separated Mordru from Violet and the Eye and later stole his amulets at super-speed. She was also the only one fast enough to evade Mordru's energy blasts, providing a much-needed distraction for the team.
Finally, the lost Legionnaires had returned to the 30th century. Jenni by this time had gotten over her crush on Cosmic Boy, but was nonetheless pleased to see him and the others. She would also remain one of the friendliest Legionnaires; she went with Triad to buy a gift for Legion liaison Shvaughn Erin's promotion and organized the girls for a slumber party, for example. Jenni would also be one of the first Legionnaires to be temporarily assigned to the Legion Outpost.
Jenni would visit the 20th century once more, this time to help the Flash and Impulse against Cobalt Blue, returning to the 30th century just in time to help the energy being who would come to be known as Wildfire coalesce.
Jenni was also the first Legionnaire to realize that Lori Morning had been using the H-Dial to become adult heroes temporarily, but kept it to herself due to Lori's pleading. However, the Dial would be discovered and taken away anyway, and Lori would reclaim it and join Leland McCauley's Workforce when it was revealed that the Legion had not even tried to get formal custody of Lori. Jenni was among the two Legionnaires (the other being Monstress) who missed Lori the most.
Jenni would also strike up a special relationship with Dyrk Magz, formerly Magno, when on Summer World, Dyrk complimented Jenni on her looks. Unfortunately, this was cut short when the Blight invaded.
Jenni was one of the last Legionnaires, alongside Live Wire, Chameleon and ally Shvaughn Erin, who remained free on the Blighted Earth. Unfortunately, she was amongst those captured when the Blight intercepted a group of refugees they were guiding to safety. Jenni was being taken to be "sapped" for her powers when she "heard" an unconscious Saturn Girl's telepathic message. Jenni was able to metabolize the fluid in her prison and free herself and Saturn Girl. Along the way, Imra transmitted the Blight's origin to Jenni's mind in the hopes that it could be used to stop the Blight. This act almost cost them their freedom, but they were saved by Cosmic Boy, Apparition, Brainiac 5, Monstress and Chameleon. The seven Legionnaires then infiltrated the Stem and stopped the Blight by freeing the Doda, a being which the Blight had been using for transport. This act reversed the Blight's state of semi-decay, causing them to disappear to dust, and the Blighted Legionnaires were freed.
When she was one of the Legionnaires left behind after many of her teammates were lost, causing the team to be forcefully disbanded, she went to Xanthu with her teammate Star Boy, where she found herself caught in a war between Xanthu and Robotica. While the two Legionnaires managed to save millions of lives by distracting Robotica long enough for the surviving Xanthuians to escape off-planet, they remained trapped there for months thereafter, until rescued by their returned teammates. Jenni then returned to active status in the Legion.
Powers and abilities
XS possesses super-speed, able to move at large fractions of the speed of light.