The Easter egg is is a trick to get iDVD to burn to external DVD drives. It requires you to put some special file in a certain location on your hard drive I believe. Don't ask me where to get it though, I don't know, you might be able to search for it.
To the original poster, no, it will not void your warrenty. It is strictly a software hack that Apple put in themselves. It cannot harm your system and Apple cannot argue that it will since it *feature* of their software.