I might have missed this, but ...
""We shot a version of this scene with Green Lantern, but the studio really fought me and said, 'We really don't want you to do Green Lantern,'" Snyder said. "So I made a deal with them, and they let me do this [instead]" Snyder expressed regret that the studio prevented him from bringing Stewart to the screen for the first time. "They were like, 'We have plans for John Stewart and we want to do our own announcement.' So I said all right, I'll give you that. So [Martian Manhunter] was the compromise," he said."