Warning: This article contains spoilers for the upcoming Warner Bros. film.
According to Entertainment Weekly, the Dark Knight and the Man of Steel both experience dreams warning of dangers to come ("including the possible appearance of DC’s galactic ultra-villain Darkseid," the magazine states, not so subtly).
However, director Zack Snyder leaves open the possibility that The Flash's appearance isn't a dream at all, but rather an attempt by the hero to cross time and space to warn Batman.
“We had such a straightforward narrative, on one hand," Snyder says, "I wanted this other layer of the movie to be complicated and bizarre."
Opening March 25, "Batman v Superman" also stars Henry Cavill, Gal Gadot, Amy Adams, Jesse Eisenberg, Diane Lane, Laurence Fishburne, Jeremy Irons and Holly Hunter.