Short answer: Flashpoint is a story about Barry Allen. Barry tries to time travel in order to prevent his mother's death. He changes the entire timeline. Superman never debuts, Wonder Woman and Aquaman lead armies that have destroyed most of Europe in their bids for world dominance, Hal Jordan never becomes Green Lantern... and Bruce Wayne dies one fateful night in Crime Alley, leading to Thomas Wayne donning the mantle of the Dark Knight and Martha Wayne going insane and becoming the Clown Princess of Crime.
There's other stuff, but it won't matter for this film.
Then what happened to the real Joker? ---
Not changing this sig until I decide to change this sig. Started: July 6, 2005