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Keaton, who played Batman in the 1989 and 1992 Tim Burton movies, is the comic book movie star trying to regain his credibility.

Stone will play Keaton’s daughter, fresh from rehab and now his assistant. Watts will be an actress in the play, while Galifianakis will play the production's conniving producer.

The other main parts to be cast include the play’s leading man and the ex-wife.

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Gonzalez Inarritu co-wrote the script with Nicolas Giacobone, Alexander Dinelaris and Armando Bo. He is producing with Robert Graf and John Lesher.

An early April production start is being eyed.

Stone is shooting The Amazing Spider-Man 2 and is attached to star in Guillermo del Toro's Crimson Peak. Watts, who worked with Gonzalez Inarritu on 2003's 21 Grams, is coming off an Oscar nomination for her performance in Summit’s The Impossible.

Galifianakis next reprises his breakout role as Wolf Pack member Alan in The Hangover Part III, while Keaton recently wrapped a turn in MGM’s remake of Robocop.

Stone is repped by WME, Anonymous Content and Ziffren Brittenham; Watts is repped by CAA, Untitled and Hanson Jacobson; Galifianakis is repped by CAA, Brillstein Entertainment Partners and Morris Yorn; and Keaton by ICM and Ziffren Brittenham.