Well, I have had an idea for a lbt fanfiction bouncing around in my head for some time. It would start out with Littlefoot and Chomper adventuring together. They find a shiny stone that they think is so beautiful that they decide to bring it back. It turns out to be a magic stone known to the sharpteeth as a Dragon's Eye Gem, and when they touch it, it splits clean in half. One half permanently reflects Chomper, the other Littlefoot.  When  the half that reflects them is pressed up against them, it will  transform them into a "warrior form"(I was thinking Godzilla for Chomper, and a  gigantic longneck with aquamancy (the ability to control water in all of its forms). If the two halves are put together, they combine forms, becoming a lung (Chinese dragon capable of swimming through the air, breathing fire, and master of water.) They would discover the joint form first, but this wouldn't come without consequences (such as Littlefoot gaining an uncontrolable desire for meat, and Chomper for certain green food.) For the bad guy, I was thinking about either a flying three headed hydra that breathes fire, lightning, and acid, a sharptooth who has harnessed the power of the stone of cold fire, or maybe both.