Got a call from a prospective client the other day with a concern that someone was creating a TV show based on a story idea she'd conceived. "You have a script, right?" I asked. Yes, she had a script. "You registered the copyright in the script, right?" was my next question. Her response, "of course." What came next was disappointing but not surprising: she'd registered her script with the WGA, not the U.S. Copyright Office.
Don't make this same mistake. Always register Scripts, Bibles, Treatments, notes from "workshops," or any other creative materials, with the U.S. Copyright Office because you cannot enforce your copyright rights without that registration. More here: https://www.copyright.gov/registration/performing-arts/