As far as I can recall, the sound came from a Swedish guy doing kind of a party trick by imitating an engine...he then recorded it, and altered the speed. The file eventually found its way out on the net, sometimes with animations added by other people. A few years later, Jamba (or Jamster, depending on where you live) picks the sound up, renders an ugly frog and voilá: the "crazy frog" was born. And I don't even think the creator of this sound got any money from it, since he never actually trademarked it or anything. :lol