SPOILER WARNING: The following article contains spoilers for Justice League, in theaters now.
Justice League's post-credits scene was leaked online earlier this week, however, this apparently wasn't the first leak of this scene. In fact, Justice League director Zack Snyder leaked details about the post-credits scene last year.
On September 29, 2016, Zack Snyder made a post on his Twitter account, in which he was dressed in semi-Batman cosplay while working on a storyboard, with the caption '#JusticeLeague #Cosplay'. A little Photoshop work revealed the storyboard to be a scene including Deathstroke, played by Joe Manganiello.
Speculation at the time of Snyder's post was that Deathstroke's inclusion in Justice League would likely be in an end-credits scene to set up his role for the Matt Reeve-directed solo Batman film. Now that Justice League is in theaters, the initial speculation around Deathstroke's appearance was confirmed as it was a post-credits scene that he appeared in, though it appears that his role in the DC Extended Universe will be on a much larger scale than was initially thought, with Lex Luthor joining him in the scene teasing the formation of the Injustice League.
Now in theaters, Justice League stars Ben Affleck as Batman, Gal Gadot as Wonder Woman, Henry Cavill as Superman, Amy Adams as Lois Lane, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, Jeremy Irons as Alfred Pennyworth, Diane Lane as Martha Kent, Ciarán Hinds as Steppenwolf, Jesse Eisenberg as Lex Luthor and J.K. Simmons as Commissioner Gordon.