Since it was made official that both Ben Affleck and Michael Keaton (and/or Christian Bale) will be appearing as different versions of Batman in The Flash movie, it was obvious that Warner Bros. is all set to introduce the multiverse in the DCEU. And if there were any lingering doubts as to whether Ezra Miller’s The Flash will be dealing with the multiverse or not, Geekosity Magazine has reported that Grant Gustin, who plays the titular superhero in the CW’s The Flash, is in talks to have a cameo in the film.
In case you haven’t read the DC comics, watched Grant Gustin’s The Flash tv series, or got the time to binge Zack Snyder’s Justice League, the Flash/Barry Allen has the power to travel through time and transport himself to different universes via the Speed Force. In the comics and tv series, Barry Allen travels back in time to his childhood to save his mother Nora Allen. But his actions displace the balance of reality and end up creating an alternate timeline where everything has changed- Barry loses his powers, his friends, and the world is in shambles.
As per the report, this is how Barry will end up coming across his other version i.e., Grant Gustin’s Flash.
The concept of a multiverse has been explored in The CW’s Arrowverse already where we have had Grant Gustin going through many time travel escapades. In fact, Ezra Miller’s Barry Allen has also made a cameo in the Crisis on Infinite Earths crossover event where he encountered Grant Gustin’s version of the character, which established that the DCEU and the ArrowVerse are both a part of the multiverse.
What further supports the possible Grant Gustin cameo is the fact that The Flash movie director Andy Muschietti has confirmed in the past that it will be presenting a unified universe “where all the cinematic iterations that we’ve seen before are valid.” In a way, it will unite all the versions of the DC characters we have seen in the DCEU to date and will possibly solve its ever-present continuity issues.
So, the fact that we have Robert Pattinson playing the caped crusader in the upcoming Matt Reeves directed The Batman while Ben Affleck, Michael Keaton, and possibly Christian Bale are returning to play the same character will somehow make sense. The Flash movie will set up a scenario that will allow them to co-exist in the DCEU and will make other future iterations of other characters a possibility as well.
As for Ezra Miller’s Flash’s powers to travel back in time, while the 2017 theatrical cut of Justice League didn’t include it, Zack Snyder’s version established that he can already travel through time. It is left to be seen whether The Flash movie will pick up after Zack Snyder’s version of the character and simply state that Barry can time travel or the character will discover it for the first time in the story.
There have also been reports of Grant Gustin doing a cameo in the upcoming The CW live-action show, The Powerpuff Girls. But nothing has been officially confirmed yet.