'The Flash' Showrunner on 100 Episodes, and Balancing Light and Darkness

The Flash sped through the 100-episode barrier tonight, making it the second of The CW's interconnected web of DC Universe shows to do so (after Arrow in 2016).

The episode saw Barry Allen (Grant Gustin) and his daughter Nora (Jessica Parker Kennedy) traveling through time, and through previous episodes of The Flash, to gather up equipment and relics they needed to battle Cicada -- giving Nora a fan's-eye-view of the history of The Flash in a way that her somewhat sanitized and simplified future never provided.

"It's a big thing," showrunner Todd Helbing told ComicBook.com at the 100th episode red carpet in Vancouver last month. "Not a lot of shows do a hundred episodes anymore, and it's 100% because of the fans that we have and the ratings that we get, so we wanted something for them, to say thank you for tuning in for five years."

That "thank you" was extended to old-time fans, too, as John Wesley Shipp's The Flash -- fromt he 1990 series -- appeared in a tag at the end of the episode, teeing up next week's "Elseworlds" crossover. Shipp's Henry Allen also appeared during a time-travel flashback.

"I think last year we deliberately tried to make it lighter and went way too far," Helbing admitted. "This year, I think you can have a darker villain but as long as the core group is enjoying what they're doing — that's season one. I think that's the magic recipe, and I think that's the perfect level of darkness. It's lighter, but Cicada's darker than probably anybody we've done in a while."

Dark as he might be, though, there will be limits: when we asked whether Joe and Cecile's baby will be off limits, even if she turns out to have powers, Helbing laughed and said yes.

"There's a limit: he does have a code," Helbing elaborated. "He doesn't kill non-metas. We'll dive into that a little bit more in the back half of the season, but we really broke this into part 1, 2, and 3, so he'll be around all season but we'll start to see other things start to happen while Cicada's going on."

The Flash airs on Tuesday nights at 8 p.m. ET/PT, before episodes of Black Lightning on The CW.