The Cone of Silence around "Man of Steel" is so all-encompassing that during Comic-Con last summer, director Zack Snyder wouldn't admit Michael Shannon was playing General Zod in the film. This despite the fact that even Shannon was discussing his take on the character as early as September of 2011. Which is why it's doubtful either Snyder or "Man of Steel" producer Christopher Nolan will ever confirm or deny this massive bit of speculation from geek site Ain't It Cool News.
[WARNING: Potential "Man of Steel" spoilers lie ahead.]
According to Ain't It Cool, famed Superman nemesis Lex Luthor will appear in "Man of Steel," though perhaps in the same way that Norman Osborn appeared in "The Amazing Spider-Man": with teasing "logos" and imagery. (Chris Cooper was eventually hired to play Osborn in "The Amazing Spider-Man 2.") Per Ain't It Cool, Canadian actor Mackenzie Gray is playing Luthor, casting made more intriguing because Gray played a Lex Luthor clone during an episode of "Smallville." Gray isn't listed on the "Man of Steel" IMDb page, however a video interview with the actor does confirm his involvement in the film.
All of this, of course, should be taken with a large grain of salt, but Ain't It Cool has broken some big spoiler-y stories in the recent past. Notably, the site revealed that a "Star Wars" spinoff focusing on Yoda was possibly in the cards, and that Jason Statham could have a role in "Fast and Furious 7." (Site founder Harry Knowles was the subject of a major profile in the latest edition of The Hollywood Reporter.) It should also be noted that "Man of Steel" screenwriter David S. Goyer was asked recently by I Am Rogue about his decision to leave Luthor out of the film, and gave this cryptic answer: "I don’t think anyone has every confirmed that we haven't included him."
HuffPost Entertainment reached out to representatives for Gray and Snyder for comment on the rumor; as of yet, neither party has responded.
For more, and to watch an interview with Gray, head over to Ain't It Cool.