Joel Schumacher's "Batman & Robin" was assumed to be a surefire hit in 1997, and screenwriter Mark Protosevich even worked out a 150-page script for its follow-up, "Batman Unchained." When "Batman & Robin" flopped, however, "Batman Unchained" was canceled, but in 2015, something akin to the latter film appeared: the video game "Batman: Arkham Knight."