Jessica Parker Kennedy as Nora Allen/XS on The Flash.

Despite Nora West-Allen’s erasure from the Arrowverse in Season 5 of The Flash, Jessica Parker Kennedy is making a return in the 150th episode of The Flash, alongside Jordan Fisher’s Bart Allen, who will make his Arrowverse debut in the series’ milestone episode. The announcement that Kennedy will be returning to the superhero series came as a surprise, so how exactly will Nora come back as XS?

In Season 4 of The Flash, Nora West-Allen came to present-day Central City in order to meet the father she never really got to know, and became part of Team Flash. At the time, she was also working with Eobard Thawne, in order to destroy Cicada’s dagger and save Barry from vanishing in a future crisis. However, after Team Flash defeated the second Cicada by administering the meta-human cure to her younger self and destroying her uncle’s dagger, Nora was erased from existence once a new timeline began to set, breaking her parents’ hearts.

Nora, along with the introduction of her brother, Bart, will be appearing in The Flash’s 150th episode later this season. It’s not yet known how or why, given that Nora no longer exists and the latter is also in the future. However, it’s possible that Nora now exists again thanks to the Crisis from "Crisis on Infinite Earths" that changed so much in the Arrwoverse. Or perhaps Bart is like his father and accidentally time-traveled, or maybe Nora ended up doing something to save herself before she was erased. But how is this happening? We have some theories about that.

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Crisis on Infinite Earths

The aftermath of Crisis left not only a different universe, and Earth-Prime, but also many different storylines and characters that were not there before. This was explained extensively in The Flash, as not only were some of the villains they had defeated now free, but they also had some new members on Team Flash. With the ever-changing storylines, it’s possible that Nora was one of those changes.

Since who Team Flash fought or didn’t fight was changed post-Crisis, the outcomes could very much be different, as well. Even if Team Flash did fight Cicada, perhaps Nora wasn’t used at all. And the other thing is that Nora came from a future where Barry went missing in 2024 due to Crisis. Since Crisis came much earlier than anticipated, and the outcome again was very different than what was described in that iconic news article, it’s also completely possible that due to Crisis coming early and Barry not disappearing, this led to Barry and Iris having children in the near future, making it possible for Nora to still be there in the future.

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Like Father, Like Son?

Another way that Nora and Bart’s arrival can be explained could be that Bart, like his father, accidentally time-traveled. It’s possible that, while training or doing something while running, he made changes that could lead to his sister not being erased. Although it’s not known how much of an influence Barry has on his son in the future, it is known that Bart is described as “the fastest teenager on the planet” and his “penchant for wildly impulsive behavior” will leave his parents stunned as they attempt to teach their son patience once he arrives in the present day. While things are being kept on the down low about this episode, it’s clear that Bart has no sense of self-control, which may be proven by his time-travel.

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Was Nora Truly Erased?

Nora first came onto The Flash in the “Crisis on Earth-X” crossover, when she was a waitress at her parents’ wedding, before it got interrupted by crazy Nazis. Throughout Season 4, she made subtle appearances, trying to get any glimpse of her father that she could. She then introduced herself as Barry and Iris’ daughter at the end of the season, and officially joined Team Flash in Season 5, helping them take down Central City’s worst criminals, including Cicada. Cicada’s defeat resulted in Nora getting erased, but is it possible it was just a time remnant and not truly Nora? Perhaps Nora was able to get back to the future before Cicada was defeated, and her time remnant was left behind. Or maybe it was her, but from a different Earth?

There are so many possibilities of how Bart comes to the present, and many more about how Nora, who is supposed to be non-existent, is reunited with her parents. Since the 150th episode is the 17th episode of Season 7, we are just barely halfway to the milestone. It’s possible that once the episode gets closer, we could be seeing subtle hints at just how Barry and Iris’ children come to the present, and why. And will they be surprised and emotional at not only seeing their son for the first time, but also their daughter, whom they thought they would never see again?

New episodes of The Flash air Tuesdays at 8 p.m. EST on The CW.

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