It was brought to my attention that a workout web page on facebook Blogilates has gotten in some trouble for posting "Hunger Games" workout videos. The post I saw said that the creator of the video believed she was protected by the "parody law." I have not seen the video but claiming protection of something as a parody can be very difficult to do. Copyright gives the creator of a work the exclusive ability to create derivative works. In layman's terms this means that the author of The Hunger Games had the exclusive right to create the movie for which I am sure the producers of the movie paid the author handsomely. But derivative works are quite a bit broader than just the movie. The author will also have to give permission to create all the Hunger Games video games, posters, action figures, and any other work based upon the books. A parody is allowed but it must be very clear that the new work is poking fun at the original work and is only using elements of the original work so that the audience knows what is being parodied.
Another issue involved here is trademark. I am willing to bet that the author of Hunger Games has a trademark or two either pending or already registered for Hunger Games. If that is the case, the owner of the trademark would object to the workout videos because it could suggest endorsement or sponsorship of the videos by the author. This is a touchy area of the law because it often causes copyright/trademark owner to go after their own fans who are very likely just trying to pay homage. But fans need to be careful before borrowing any elements of their favorite works because they may be in for a nasty surprise.