As is often the case with Allen, plot details are being kept under wraps. The movie marks both Posey and Blackley's first time working with the director. Posey, a veteran film and TV actress known for her quirky sense of humor, would seem a natural fit for an Allen project.
With regard to Blackley, Allen has a track record of working with young Hollywood's most sought-after actors: Stone, of course, is also starring in his "Magic in the Moonlight" (opening Friday), and in the past decade Allen has also cast Jesse Eisenberg, Ellen Page, Evan Rachel Wood and Scarlett Johansson in lead roles.
Blackley, however, is not yet a recognizable star. His first major exposure to American moviegoers will come next month in "If I Stay," the tearjerker based on Gayle Forman's bestselling young-adult novel. The 23-year-old plays Chloe Grace Moretz's older musician boyfriend in the picture, which hits theaters Aug. 22.
Blackley, who had a supporting role in 2012's "Snow White and the Huntsman," previously showed off his musical talents in a stage production of "Spring Awakening" in his native England.