The Flash is bringing back a surprise character for its upcoming 150th episode milestone. (Spoilers Follow) A new article reveals that Nora West-Allen (Jessica Parker Kennedy) will be making an appearance in the 150th episode of The Flash - and she won't be the only child of Barry Allen/The Flash (Grant Gustin) and Iris West-Allen (Candice Patton) showing up. Bart Allen (To All the Boys: P.S. I Love You's Jordan Fisher), Nora's brother from the future will also be making his debut in the 150th episode, and what we know so far is that the two speedster siblings will "cross paths."
EW's feature about The Flash episode 150 doesn't provide any further details about what's going on in The Flash episode 150. However, last month's announcement about Jordan Fisher being cast as Bart Allen came with a character synopsis that provides more details, which now make more sense:
"Bart is the fastest teenager on the planet. But due to Bart's penchant for wildly impulsive behavior, stunned parents Barry and Iris will have their hands full trying to teach their new son patience. But it's a task they'll have to accomplish in order for their family to work together and stop Team Flash's biggest threat yet!"
So, as you can see above, The Flash episode 150 will require a big West-Allen family team-up to stop a big threat - one big enough to seemingly bring Nora back from the dead.
Nora West-Allen first showed up in The Flash season 4 as a mystery character who was seen hovering around key events for Team Flash (like Barry and Iris' wedding during "Crisis on Earth-X"). It was at the end of season 4 that we learned who Iris really was, as Nora helped her dad destroy the S.T.A.R. Labs satellite and stop The Thinker/Clifford DeVoe's "Enlightenment." In The Flash season 5, her character arc as "XS" revealed that Nora was raised by Iris after Barry was thought dead, and she was trained by Eobard Thawne (Tom Cavanagh) to use speedster powers and travel back in time. However, Nora's time travel screwed up the timeline, resulting in the villain Cicada causing even more havoc and death. In the end, Nora had to help Team Flash stop two versions of Cicada (including one from the future), which resulted in Nora being erased from the timeline.
Of course, The Flash telegraphed in season 6 that there are possible futures or other states (Speed Force) that Nora may still exist in. We'll see which reason the show uses to bring her back.
The Flash episode 150 is currently beginning production in Vancouver. No specific air date has been given yet.