Pink Tentacle tells the story in more detail (and more coherently) than I, but the gist is that Yanobe Kenji, who we've mentioned before, created this for Disneyland's 50th anniversary exhibition...but it didn't crank Disney's tractor.
We think this is a huge missed opportunity. Disney characters already appear in Kingdom Hearts, right? Now they have a chance to appear in Fallout! See? It's genius. Somebody pay me.