How does copyright affect spoofs or parodies?

If your spoof is a true parody, you are protected under the "fair use" doctrine from a claim of copyright infringement. However, it is very tricky and difficult to decide if you really are creating a parody. A parody, according to the United States Supreme Court, "is the use of some elements of a prior author's composition to create a new one that, at least in part, comments on that author's works". For some examples of successful parodies, check out the "Pretty Woman" song parody in the case Campbell v. Acuff-Rose Music, Inc. and the case of Suntrust v. Houghton Mifflin, where the appeals court upheld the right of Alice Randall to publish a parody of Gone with the Wind called The Wind Done Gone, which told the same story from the point of view of Scarlett O'Hara's slaves. On the other hand, fair use was denied and infringement found in the case of Dr. Seuss Enterprises v. Penguin Books case, where the appeals court found that a satire of the O.J. Simpson murder trial and parody of The Cat in the Hat had infringed upon the children's book because it did not provide a commentary function upon that work. You should check with someone familiar with copyright law about whether fair use would be a defense in your case.