Batman: Arkham Knight has been the subject of numerous rumors regarding its cast. You shouldn't believe any of them, though.
The latest rumor is that Batman: Arkham Knight will include Damian Wayne, Nightwing, Robin, Azrael and even Superman. The source of the rumor is a screenshot from IMDB's Arkham Knight listing:
The credits seem credible enough because they list voice actors who have worked in the DC universe before. Scott Menville, the man supposedly voicing Robin in Arkham Knight, played that character in Teen Titans. Arkham Knight's alleged Superman, George Newbern, was the Man of Steel's voice in Injustice: Gods Among Us.
Here's the problem, though: anyone can edit an IMDB listing. It takes about a minute to set up a free account for the site and another minute to attach an actor to a project.
While this information has to be approved by IMDB's "data-editors," keep in mind that the site has close to 3 million titles and 6 million people in its database. That's a huge amount of information to maintain so a semi-credible listing like George Newbern voicing Superman on Arkham Knight is likely to get approved even if it's bogus. The fact that this casting information hit IMDB in the first place and then got scrubbed after the fact shows that the goalie occasionally misses a few pucks.
This isn't the first time that new characters were "confirmed" for Batman: Arkham Knight due to IMDB. Back in May, Killer Moth and Bane were spotted on the site's listing for Arkham Knight:
Who's adding characters like Azrael or Superman to Batman: Arkham Knight? Well, whoever it is, they don't work for the game's developer Rocksteady Studios.
"Hmmm there's certainly no-one here at Rocksteady who's updating the IMDB for our game, so I'd take anything you find on user-generated sites with a healthy dose of skepticism!" said Arkham Knight community manager "CODA" with regards to earlier character rumors in April. That previous group of rumored characters included Hush, a.k.a. Thomas Elliot. Again, that gossip started with an IMDB listing.
This isn't to say that IMDB's at fault. Their user-driven system allows the company to offer detailed information on a broad range of projects. As I said, the size of the database makes it impossible for them to be completely accurate at all times. However, if some website's claiming that Killer Moth or Superman's going to be in Batman: Arkham Knight and their only evidence is a screen-cap from IMDB, they deserve as much skepticism as you can muster.