The soul of the Skorr was stolen.

For no reason whatsoever today, I’ve started thinking about expanded universes in sci-fi.

To put it in very general terms, the expanded universe is something that exists outside the mainstream of the show/movie/etc. Expanded universes can be fan-created, done outside the system that owns the original universe, or even created by someone associated with the original property. A lot of expanded universe isn’t canon, meaning the creators or rights-holders of the original thing don’t recognize it as official. But some of the expanded universe stuff is considered canon — the Star Wars novels and games, for example.

Thanks to the expanded universes, whatever the fuck is happening here is considered canon as far as Star Trek is concerned:

There’s good expanded universe sci-fi and awful expanded universe sci-fi. What’s your favorite awful stuff (more points if it’s recognized as canon)? And what’s your favorite really decent expanded-universe property (points if it’s non-canonical)?