Trivia: Kingdom Come
- Actor Allusion: In a one-panel cameo, The Joker looks just like Jack Nicholson in the Tim Burton Batman movie. This is a general rule for all Alex Ross publications that feature The Joker. Likewise, Alex Ross clearly looked up what Frank Gorshin looked like as an old man in order to draw The Riddler.
- What Could Have Been: The sequel The Kingdom was originally planned to be a prequel which takes place between the "present" main continuity and the "future" in Kingdom Come. Another source say the sequel would reveal the Kingdom Come universe to be the post-Crisis version of Earth-Two, which was altered rather than erased from existence.
- If it's true, then they changed their minds so late that they couldn't completely remove that plot thread from the story as The Kingdom is bookended with Superman of Earth-2 pounding on the walls of reality.