Everything is a Remix (previously) is an important, entertaining series of short videos that trace the ways the creation is built on earlier creation — that "originality" is just mixing existing things in new ways.
In the latest EiR video, creator Kirby Ferguson covers Fair Use, the key legal principle that allows users of copyrighted works (including other creators) to use some (and, in some circumstances) all of a work for critical, transformative, or satirical purposes.
Ferguson ends his video with a very cautious three-step test to see if your use might be fair. It's good advice, but that's not all it is — fair use is a lot more expansive than that. He invites viewers to send him questions about fair use and promises to follow up by asking a "real live lawyer" the thorniest of them.