The Evil Crossover from Hell: The Watcherverse came about thanks to a game at Connotations. I'm blaming them.
The short version is that Watcherverse is a collaborative universe which combines a number of different fandoms. It is mostly slash although not exclusively and will probably contain some adult content down the line. You have been warned!
Welcome to the Watcherverse. This crossover universe takes the concept that the Watcher organisations in different canons are actually part of the same body - the different divisions just don't know about each other. It grew from there with other works being added in anywhere they could be logically made to fit.
See the LJ community for more details.
How does a fandom get added into the 'verse?
Easy - propose it, explain the justification and points of interaction. If you make a good case then it will get added in. Part of the fun here is to deviate as little from canon as possible while still adding to the great mindfuck that is Watcherverse.
How does a pairing get added into the 'verse?
Okay - I will confess that I have a few preferences pairing-wise, don't we all, however I want to be fair about this. So...
1. For now the person who ties in the fandom or writes the story gets to set the nominal pairing(s). As people join in then where there are community-recognised 'that should be canon stories' they can be voted in as canon. I don't know all the fandoms in the list - I don't think one single person can (especially as the list grows) so different people will become responsible for keeping track of the 'canon bible' for different sections.
2. If a pairing get added into official Watcherverse canon that is not the end - you can still write whichever pairing you like and post it here just make it AU