One of the most challenging things about your creative work, whether it's a literary piece, a song, or a film, is protecting what you've created. The way to protect it is by copyrighting it.
You can register your work with the United States Copyright Office, and, of course, there is a fee. If you register your work online, however, and upload a digital copy, the registration fee is only $35.00. Using the regular system, I believe the fee is $65.00. I've never used the regular system, so I can't vouch for it.
I have used the online registration for every single one of my novels and stories. By registering your work, and obtaining a copyright, you have something to defend yourself if something ever comes up with someone stealing your work, and saying they created it first. If your can show the date your project was registered, you can invite the other person to go...uh...climb a tree.
Keep in mind: You can't copyright a title. You can't copyright a name. You can't copyright a trademark.
The web address is: www.copyright.gov
Michael (T. M.)