Robin Hood is another example of a set of works that had many people contributing different stories into what became the present-day collection.

Historically, a lot of works had many authors using the same character. I think that it’s a bit unfortunate that modern copyright law tends to discourage that.

H. P. Lovecraft was unusual in that he allowed other authors to make use of his characters (and settings, which are also covered by copyright), which is why his world – with Cthulhu and all that – has been widely used.