How The Flash Movie Can Explain Robert Pattinson as Batman's Role
The Flash movie is likely going to include Michael Keaton as Batman, reprising his role as the [...]
It Brings Him To The DCEU

One theory which some fans will certainly hope for is Matt Reeves will see his Batman movies ultimately tied to the events of the DCEU after Flashpoint. Flashpoint has an opportunity to bring heroes from alternate worlds together, thus explaining the recasting of Ben Affleck's Batman as Robert Pattinson.
This comes with more than a face transformation. An alternate world's Batman also comes with a whole new story. The Batman trilogy is going to be an origin story, explaining how Pattinson's Bruce Wayne becomes Gotham's Dark Knight. After he comes Batman in the first film of the trilogy set for release in October of 2021, Pattinson's version of the character could then be introduced to the other DC heroes through Flashpoint and go forward existing in their universe.
An opportunity for an origin story to be told in regards to Batman within the DCEU is certainly an interesting notion, bringing a younger version of the hero into mix after Affleck's portrayal of a hardened and grizzled Batman was the original plan.
It does, however, seem more likely that Pattinson's version of the character will remain an isolated taled, so...
prevnextIt Acknowledges Multiverse Existence

What's more likely is that Flashpoint briefly acknowledges the existence of Pattison's Batman. Reeves seems interested in telling his own story, completely free of constraints which a larger universe puzzle could impose on his options. If the filmmakers choose this route, it would seemingly be a purely for the sake of fan service play, but a quick appearance by Pattinson's Batman in a sequence which shows the many existing Earth's and universes could be enough to satisfy some tough critics.
This way, Pattinson's Batman has the opportunity to continue his story without any sort of implications from The Flash movie, aside from maybe his world ending for a moment.
Grant Gustin's Barry Allen briefly met Ezra Miller's Barry Allen, something which won't massively impact the journey of Miller's version of the character but is something the filmmakers had to keep in mind while crafting the story. It remains to be seen if this is the moment which sends Barry down the rabbit hole of opportunities to save his mother Nora Allen from dying when he was young but it could be a similarly small moment for Pattinson's Bat.
prevnextIt Doesn't

The other route is much more simple. The Flash movie does not have to acknowledge Pattinson's Bruce Wayne in any way. For some this may be disappointing. However, looking back at how well Christopher Nolan's Dark Knight trilogy performed without any connections to other DC Comics characters, it may be in the best interest for Reeves and company to simply tell their story, fully realize Gotham and the Batman characters, and leave the crossover for the rest of the films, casts, and stories.
The multiverse will exist and this opportunity will remain further down the line, should Reeves, Pattinson, or anyone else become interested in having the new Batman interact with the rest of the DC characters on film.
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