CAA has signed Michael Bacall, the comedy scribe who wrote “Project X” and “21 Jump Street” — the latter of which has grossed more than $88 million worldwide to date.Bacall, who is writing a treatment for Warner Bros.’ “Project X” sequel, has also signed on to pen a “21 Jump Street” sequel for Sony once he collaborates with star Jonah Hill on a treatment. “Project X” producer Todd Phillips is also producing Bacall’s original script “Psycho Funky Chimp,” about two obsessive collectors of rare Pez dispensers. Scribe is currently adapting Neal Bascomb’s novel “The New Cool” for producer Scott Rudin, having recently adapted Richard Aleas’ pitch-black detective tale “Little Girl Lost” for Marc Platt Prods. at Universal. Bacall is also working with Red Hour Prods. to develop a comedy about Tom Cruise’s “Tropic Thunder” character Les Grossman for Paramount. Bacall continues to be repped by attorney Jeff Shumway of Timaeus Group.