The copyright for the original versions of Winnie the Pooh and Mickey Mouse have expired. Now, members of the public can create—and are busy creating—their own works based on these beloved characters. The law is clear: if you have a Winnie or Mickey story to tell, feel free to do so.

Suppose, though, that we’re not inspired by Winnie or Mickey. Let’s say we want to tell stories using Batman. The copyright on the original Batman comic does not expire until 2035. To what extent can we use Batman and rely on the fair use doctrine?