Image via WikipediaExpanded universe (n.) - Stories set in a fictional universe that occur outside the franchise's original medium, such as comics that tie into a popular movie, or novels that are set in the universe of a popular television or video game franchise. The Star Wars expanded universe is the seminal example, largely because George Lucas maintains such tight control over its content, though Star Trek, Doctor Who and Buffy the Vampire Slayer also maintain healthy and successful expanded universes.
I bring it up because: LucasFilm has confirmed at least two more mainstream Star Wars expanded universe projects, a Star Wars sitcom from Seth Green and the Robot Chicken guys, and an animated series chronicling the post-Jedi adventures of Han, Luke and Leia. This doesn't even touch on the news that Joss Whedon may be writing and directing the Avengers movie, which plays off the highly successful Iron Man movie continuity, including Iron Man 2 which opens May 7. It's fair to say that a great many more people saw Iron Man the movie than have ever read an Iron Man comic, and Marvel's plans for a cohesive movie continuity between Iron Man, the Incredible Hulk, Thor, Captain America and The Avengers will pull equally one-sided numbers. This begs the question, which is the expanded universe: The Marvel movies, or the Marvel comics?