h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Once upon a time there was an old man from a cold country and his name was Propp. Vladamir Propp.

Now Propp had an idea and decided to write it all down in a book. He called this book "The Morphology of the Folktale". In this book he stripped the idea of the classically structured story or folktale into small parts. When he counted up all these parts he had 37 (if I remember correctly).

Within these 37 parts Propp could fit any plot point from a story, and within these plot points he could fit his characters. But, like his plot points, there weren't an infinate number of characters. Only a possibility of 7 character types (or a mixture from within that 7).

And from this book came the idea that a film student could write his thesis, extending Propps ideas into film and using Star Wars as an example. But that's another story...