The online pass system seems to be everywhere, even in single-player games. According to Eurogamer, Warner Bros. Interactive have confirmed that an online pass will be needed to access the Catwomen content on the Batman: Arkham City disc.
“Further to your story, players who purchase previously owned copies of Batman: Arkham City can access the playable Catwoman content for £7.99/ 800 Microsoft Points,” said a Warner Bros representative. “Playing as Catwoman is not required to complete the game.”
However, without the code, Catwoman still appears in the game as part of the story, but her playable missions remain locked. In addition, it also unlocks Catwoman as a playable character in the challenge missions.