What Is Fair Use?
http://fairuse.stanford.edu/Copyrigh...pter9/9-a.html
2. Parody
A parody is a work that ridicules another, usually well-known work, by imitating it in a comic way. Judges understand that by its nature, parody demands some taking from the original work being parodied. Unlike other forms of fair use, a fairly extensive use of the original work is permitted in a parody in order to "conjure up" the original.