Not for the first time, a fan has put together a pretty impressive trailer for a live-action adaptation of Flashpoint, the comic book miniseries that inspired Justice League: The Flashpoint Paradox and seems poised to be a central focus of The Flash's third season.
You can check it out above. It features audio from the animated Flashpoint Paradox movie along with (often digitally-altered) video from The CW's DC Universe shows, Batman V Superman: Dawn of Justice, Green Lantern, and more.
Flashpoint was a five-issue miniseries written by Geoff Johns and featuring art by Andy Kubert. It told the story of an alternate universe where there was no Superman or The Flash, Wonder Woman and Aquaman's nations were on the brink of war, and Batman was Thomas Wayne, driven to the edge after the murder of his son in Crime Alley.
With the world hanging in the balance as a dark and ultra-violent war between Atlantis and Themyscira plunged parts of Europe into the ocean, Barry Allen was the only one who could remember the pre-Flashpoint world, and had to work to restore his powers so that he could travel back in time and fix it.
The big twist, for those who don't know it, is that the terrible, near-apocalyptic timeline was the result of Barry Allen traveling back in time to save his mother from being murdered by the Reverse-Flash.
The Flashpoint storyline was, in its most basic terms, adapted into an animated feature film titled Justice League: The Flashpoint Paradox. It's one of the best-reviewed and best-regarded of the DC Universe animated movies, and certainly worth checking out.