This is an excellent tutorial by Andrew Kramer of Video Copilot. He goes through using Keylight (which is otherwise an impossibly obtuse effect in After Effects). These tutorials have really helped with the compositing on Pandora Machine movies.
It's spelled "HACBM" but pronounced "Nasvoom". I know, it doesn't make any sense to me either.
This is a test of an idea for a test. I have no idea how Tyrannosaurus Mouse would play it, nor do I know what the "B" section would be. I don't know what the "C" section would be either, if it comes to that. We'll try it. Maybe we'll figure out something.