wikipedia zu shared universe: "A shared universe is a fictional universe to which more than one writer contributes. Work set in a shared universe share characters and other elements with varying degrees of consistency. Shared universes are contrasted with collaborative writing, in which multiple authors work on a single story. Shared universes are more common in fantasy and science fiction than in other genres. Examples include the Star Trek, DC Universe, Marvel Universe, Star Wars, Forgotten Realms, Man-Kzin Wars, and Cthulhu Mythos."