If copyright only extends to actual "fixed" works and not ideas, then it seems to me that copyright should not extend to the concept of characters. A character is no more than an idea once you divorce it from the underlying fixed text. That is in fact one of the primary falsehoods in copyright law - any derivative work that does not contain an actual clone of the fixed underlying work is merely borrowing from an idea, not the protected fixed work itself. Ideas can admittedly have varying degrees of abstraction, and a fictional character is certainly less abstract than many other forms of ideas - but that does not change the fact that it is still just an idea. All literary ideas remain ideas until they are written down (or "fixed" as the law would say). Once it is written, the idea remains an idea. The copyright should only extend to the concrete writing itself. The entire concept of "derivative" works destroys the fundamental compromise behind copyright philosophy.

Unfortunately, the courts have never recognized this obvious falsehood. If X creates a suave spy named "James Bond", then all future authors are prevented from using a suave spy character named James Bond, even if they never actually copy from the previous works that Bond has appeared in. They may even be prevented from creating a spy character with a different name, but still happens to dress sharp and enjoy vodka martinis that are "shaken, not stirred" (since many would naturally identify such traits with the Bond character),

So what happens when the courts blur the distinction between ideas and fixed works? You get ridiculous lawsuits like this one - where Carol Burnett sues somebody for drawing an animated character wearing a blue bonnet, bucket and mop. Maybe even depicting janitors tugging on their ears is now off-limits.