Warning: There are spoilers for Batman v Superman: Dawn of Justice ahead!
After over a year of rumors, it’s been confirmed several times over the last few months that Ezra Miller’s Flash will make his DCEU debut later this month in Batman v Superman: Dawn of Justice. Early reports stated that the Scarlet Speedster might just appear as a blur while foiling a crime, but now it’s been revealed that, for at least one moment in the movie, he’ll be seen in one of the movie’s dream sequences.
In the midst of the two eponymous heroes doing battle and all the other events, Batman v Superman: Dawn of Justice will have Flash appear in one of Bruce Wayne’s nightmares to deliver a "cryptic message." However, it will be left ambiguous whether this was really DC’s most famous speedster warning Bruce Wayne or just part of the dream. Director Zack Snyder elaborated to EW:
We had such a straightforward narrative, on one hand, I wanted this other layer of the movie to be complicated and bizarre.
It’s been said before that Flash, along with Aquaman and Cyborg, are basically just cameoing in Batman v Superman: Dawn of Justice, but this dream sequence he shows up in sounds a lot like the Knightmare. In nearly all of the previews, we’ve seen a desert-geared Batman in a post-apocalyptic looking world (most likely Earth) where a corrupt Superman reigns supreme. Then in January, an image came out of Batman overlooking the ruins of a city, and burned into the ground was a giant Omega symbol, foreshadowing the coming of Darkseid and proving that this isn’t a mere dream one gets from eating too many late night tacos. It’s assumed that this Knightmare will only further fuel Bruce Wayne’s paranoia towards Superman, thus leading to their conflict. The possibility of Flash somehow traveling back through space and time to warn Bruce, if that truly is what happens, is also an intriguing one, and also shows the regular moviegoing audience that he’s a guy who can do more than just run quickly.
The Knightmare will be just one of several dreams of "dangers to come" for both Batman and Superman, and Snyder called Flash’s appearance a "a giant Easter egg," which he hopes will get fans speculating online. However the events of Batman v Superman: Dawn of Justice unfold, Flash will officially team up with the movie’s other heroes in 2017’s Justice League: Part One. He’ll then lead his own movie in 2018, and the year after that, he’ll be a team player again in Justice League: Part Two. This dream cameo is just something to get people scratching their heads while the main story progresses normally.
We’ll see Flash on the big screen for the first time (not counting that cameo in The LEGO Movie) when Batman v Superman: Dawn of Justice arrives on March 25.