Zack Snyder's Justice League - Easter Eggs & Hidden Details

General Swanwick, a character present since Man of Steel and played by Harry Lennix, is revealed to be the shapeshifting Martian hero J'onn J'onzz, also known as the Martian Manhunter. He first appears disguised as Martha Kent to console Lois Lane, and later reveals his true form to Bruce Wayne, offering his help for future threats. This was part of Snyder's long-term plan for the character.

Dr. Ryan Choi, a scientist at S.T.A.R. Labs, has a significant supporting role. In the DC Comics, Choi is the third person to take up the mantle of The Atom, a superhero with the ability to shrink. His promotion to Director of Nanotechnology at the end of the film hints at this future.

During the flashback to Darkseid's first invasion of Earth, a member of the Green Lantern Corps is seen fighting alongside the Old Gods, Amazons, and Atlanteans. This Lantern is identified as Yalan Gur, the protector of Space Sector 2814 (which includes Earth) from the comics. Another dead Green Lantern is briefly visible during Cyborg's Knightmare vision.

In the Knightmare epilogue, the Joker taunts Batman by asking, "...why you sent a Boy Wonder to do a man's job?" This is a direct reference to the death of Robin at the hands of the Joker, an event previously hinted at in Batman v Superman by the defaced Robin suit in the Batcave.

Zack Snyder is a known admirer of Ayn Rand's novel The Fountainhead. An architectural drawing in Lex Luthor's home is for the "Security Bank of Manhattan," a reference to a project in the book. Additionally, a sinking boat is named "The Cortlandt," another reference to a housing project from the novel.