Since the mid-1990s, Walker wrote several screenplays that were never greenlit or have yet to go into production, such as a script for a movie starring the superhero Silver Surfer, a version of "X-Men" (2000; his script was written in 1994), and a film tentatively titled "Batman vs. Superman". The latter film was set to go into production, but Warner Bros. opted to revive their franchises separately, and so the script was shelved. After the announcement and subsequent successes of "Batman Begins" and "Superman Returns", the film seemed to be shelved permanently, though Wolfgang Petersen, who was due to direct the feature, had continued to express his interest in the project. That script and version of the project was permanently shelved in favor of the Zack Snyder helmed "".