It’s the one between comics and television of course! This falls under a category called Transmedia, because it goes from one to the other and on to another. That’s a strange and vague description that is better explained with an example (or how about three).
- Buffy the Vampire Slayer (and Angel as well) was first a TV show; when the show ended they started writing comics. There are also action figures, but I’m not sure where those fall on the standard of media.
- Another: Beauty and the Beast was a Disney movie, a TV show (in 1987), a Broadway musical, and a TV show again (premiered this season).
- My favorite: Doctor Who was TV show in the 60’s, then branched into comics, audio books, and video games, and was then relaunched as a TV show in 2005. This is the fandom that will never die!
There are countless examples of this, but a common thread is that each of these examples (and countless others) was first one thing and was quite popular in that medium. Then it was expanded to include other mediums. This occurs for both economic and fan-ish reasons.
Of course the company that created the original media wants to get the biggest profit from it, so they capitalize on it. They create all sorts of new ways for fans to interact with the story (by buying their products).
It also happens for reasons of awesome. Fans want more. As much as the corporations are going for the capitalist side of the media, if there isn’t a market for it, they know better than to try. That means that fans (that’s US!) demanding things to exist can help them start to exist. If we want something to exist (even something like The Hawkeye Initia… that may not be the best example) we can make it happen.
In the same way good-but-unknown things feed the imagination and creativity of creators leaving us with things like Sherlock, The Dark Knight, The Lizzie Bennet Diaries, our favorite fictional characters on Twitter, and The Avengers.