While Marvel pursues a completely integrated single universe (barring the Fox franchises), DC has gone the other way with its films and shows – establishing a ‘multi-verse’ like the comics which allows for disparate productions to exist and, in the case of “The Flash” and “Supergirl,” crossover if the opportunity allows.
With that established, it makes sense that Warner Bros. Pictures will keep its DC film universe separate from its DC TV series – which is why Ezra Miller is playing a different incarnation of The Flash in the upcoming “Justice League” films than the one Grant Gustin plays on The CW’s “The Flash” series.
Speaking about that decision, the film’s director Zack Snyder tells NY Daily News the reason Gustin’s version wasn’t used was both to avoid confusion and due to the differing tone:
just don’t think it was a good fit. I’m very strict with this universe and I just don’t see a version where…that (tone is) not our world. Even if Grant Gustin is my favorite guy in the world and he’s very good, we made a commitment to the multi-verse (idea), so it’s just not a thing that’s possible.”
This would suggest the upcoming “The Flash” film won’t have the same light, sci-fi and endearing tone of The CW series. Seth Grahame-Smith helms the new “Flash” which is currently targeting a March 2018 release. Gustin’s version of The Flash pops up on “Supergirl” on March 28th and Warners has just released the promo trailer for that crossover below: