never never land or public domain?

Peter Pan is property. Or is he? When does an artistic creation become part of the public domain? Does that depend upon its time and place of creation? Publication? Whether or not the expression was used in a series of works, spread out over time? If one of those later works is still under copyright?

The Standford Law School Center for Internet and Society is representing the author of a book that involves a modern day rescue of Peter Pan from Neverland. Will the Center be able to save the author and Peter Pan from Never Never Land? They filed a complaint for declaratory judgment in a California Federal Court on December 20th, asking the Court to hold that Peter Pan is in the public domain in the United States, and to enable Emily Somma to have her book published.