Complex sentence: In 2013, Stone signed on to co-star in Alejandro Gonzalez Innaritu's black comedy-drama "Birdman" with Michael Keaton and Edward Norton, as Sam Thomson, the recovering-addict daughter of actor Riggan Thomson (Keaton), who becomes his assistant.
Split into simpler sentences: In 2013, Stone signed on to co-star in Alejandro Gonzalez Innaritu's black comedy-drama "Birdman" with Michael Keaton and Edward Norton. She played Sam Thomson, the recovering-addict daughter of actor Riggan Thomson (Keaton), who becomes his assistant.