The Season 4 finale of The Flash left fans with plenty of mysteries to ponder throughout the hiatus, although it did answer the big question of the Mystery Girl's identity. Mystery Girl is -- as many speculated -- the daughter of Barry and Iris from the future. Nora West-Allen will undoubtedly have a significant part to play in Season 5 when The Flash returns, and one Flash actress has teased that a crossover could be in store for Barry and Iris' daughter. Danielle Nicolet and Jessica Parker Kennedy, who play Cecile Horton and Nora West-Allen, respectively, recently appeared at a convention, and Nicolet had this to say:
I was really excited to pop over to Supergirl for five seconds last season and I don't think I'm spoiling anything to say there are going to be more crossovers this next season. Yes, there is a very strong likelihood that one or two people at this table - maybe both - will be crossing over.
Every year since The Flash joined Arrow in The CW's superhero lineup, one big multi-show crossover has aired in the fall, and a number of mini crossovers have taken place as well. Now that Legends of Tomorrow and Supergirl have joined the Arrow-verse (although Supergirl technically takes place over on Earth-38), there are plenty of opportunities for Arrow-verse characters to pop over to other shows, and Danielle Nicolet's comments to media (including Express.co.uk) at the MCM Comic-Con seem to point toward both Cecile Horton and Nora West-Allen crossing over to shows other than The Flash in the 2018-2019 season.
Of course, Nora (and Cecile) appearing in a crossover doesn't mean that the crossover will be all about that character; the big "Crisis On Earth-X" crossover pulled out all the stops and delivered the majority of the significant Arrow-verse characters in one hour event. A crossover with Nora could be as simple as Nora popping up on Arrow or Legends of Tomorrow rather than playing a pivotal role in the big crossover event. Given her status as a time-traveler, Nora could be a good fit to appear on Legends of Tomorrow, which will be short a speedster in its fourth season anyway.
Jessica Parker Kennedy also commented on the prospect of appearing in further Arrow-verse crossovers as Nora, saying this:
I think crossovers are the coolest. The very first episode I did was a crossover and it was awesome and everyone was there and everyone was in a good mood. I feel like it's so fun to do that.
Arrow-verse viewers got their first look at Nora West-Allen -- then only known as Mystery Girl -- when she appeared in the first leg of the "Crisis On Earth-X" crossover as a young woman who seemed strangely invested in Barry and Iris tying the knot. While her scene was tiny in the grand scheme of the Earth-X Nazi invasion, it led to a major plot on The Flash. It would be fun to see more of her in future crossovers, especially if Barry has to introduce her to his super pals as his daughter. The look on Oliver Queen's face alone would be worth any leaps of time travel logic that made Nora's arrival possible. Maybe Arrow's Emily Bett Rickards could get her wish for a female-centric episode!
The Flash will return to The CW with new episodes in the fall. In the meantime, swing by our picks for what The Flash should change in Season 5, our five best theories about the mysterious Thomas, and our rundown of eight Flash mysteries that never got explained in Season 4. If you're in the market for shows to watch during hiatus, check out our summer TV premiere guide.