The ending hasn’t been written yet, but Hollywood is moving quickly to bring the story of the GameStop investment saga to the screen.Separate projects at Netflix Inc. and Metro-Goldwyn-Mayer Inc. are already in development over the past week on Wall Street, in which an investing-focused group on reddit message boards got together to skyrocket the share prices of struggling companies such as GameStop Corp. and AMC Entertainment Holdings Inc., in the process crippling the hedge funds that had bet against them. Netflix is in talks with screenwriter Mark Boal, who dramatized real-life events such as the Osama bin Laden raid in “Zero Dark Thirty” for a movie that would include the streaming company’s breakout 24-year-old star, Noah Centineo.At MGM, executives are planning to develop a forthcoming manuscript by Ben Mezrich regarding the saga titled “The Antisocial Network.” The studio moved so quick that it obtained the rights to Mr. Mezrich’s book proposal, which is being shopped to publishers to acquire this month, according to a person familiar with the deal.