I've been reading about Alexandre Dumas.
Dumas ran a fiction factory- churning out novels in serial form for the popular press. His many collaborators included a man called Maquet, who wrote the outlines for Dumas' most famous works- The Three Musketeers and The Count of Monte Cristo.
Critics tend to be a bit sniffy about this kind of operation. It subverts the romantic cult of the artist as creative demi-god and loner.
But popular fiction has always been produced like this. The Iliad and Odyssey are the work of many hands; so- to a lesser extent- are Shakespeare's plays. And when we come to the modern era, cinema and TV are essentially collaborative .
Dumas was doing much the same thing as a writer-producer like Joss Whedon or Russell T Davies. He is the author of the Three Musketeers just as Davies is the author of Doctor Who. The concept is stamped by his presiding imagination even though much of the work was done by someone else.