Funny thing, though. This is the problem only in the US, to my knowledge. in Japan, the creator always has shared rights with the publication and animation firms that distribute their work. It is common to pick up a toy package and see a long list of copyright on it. Say you pick up a Dr. Slump doll... the back would have (C) Akira Toriyama/Shuiesha/Toei Animation.I know, it's true. I wish there were more rights for the artists themselves. The world is not always a perfect and just place, by its very nature (or rather by ours, heh). We should try our best to improve it, but there will always be problems such as this. Despite all that, it would be worse if the artist was officially entitled to nothing, ever. As flawed as this system is, the alternative (no copyright laws) would be unexceptable.
And here's another interresting tidbit. They have a copywrite loophole that allows for actual published fan versions of other people's work. There are a lot of specifics, one being the run has to be very small, and the story will not be widely accepted as the product, and certain companies won't allow it. But other than that you can actually publish a fan work based on someone's idea. Sadly, it's used more for porn, though. but an excellent example of a story driven fan work is a Doraemon fan comic that gives a hypothetical ending to the series.
Too bad we could never have anything like that here. I'd give you guys some fan made Pigs in Space comics.