It's Not Easy Being Green

I dunno where the butterfly-flaps-its-wings thing comes from, but the genesis of the 'butterfly effect' is a story Ray Bradbury wrote in which some dudes travel back to, like, the Jurassic Period. They travel a set path so that they don't affect anything, but one of them goes off the path and accidentally steps on a butterfly. When he gets back to the future, he realizes that a lot of things have subtly & unexpectedly changed.