What's cool about it as an in-joke is that it even works in-universe. No reason Star Wars couldn't really exist as a fictional franchise in the past of the 'Verse. It could still have fans even in that far future (I can see Wash being a big fan of it). Alternatively, cultural tropes can be distorted greatly over the centuries; maybe the Carbonized Han Solo figure has become the icon of a religious cult, like the image of Christ on the cross. Though in that case it's harder to imagine who it would belong to, since Book is pretty clearly a Christian and there's that commandment about graven images. Maybe that's why it keeps moving around the ship -- to keep Book from getting rid of it. Although Book's a pretty tolerant guy, except where pedophilia and talking in the theater are concerned.
