Moon has it right. Wolf's work on this is the equivalent of an illustrator commissioned by, say, Disney to create illustrations of previously trademarked and copyrighted materials. In that case, the illustrator owns no rights to the finished piece; it is strictly "work for hire". The fact that Wolf is creating a 3D version is irrelevant -- an illustrator would be doing the same thing in 2D and, at the end of the day, would own no more rights to the work than Wolf will. You are not a "creator" for this piece in terms of the copyright law, because the "creation" has already been done. Scott's advice is the best course in cases like this: charge a fee, then charge as well for each subsequent animation.