Walken, Farrow & Blair Join The "Dark Horse" Christopher Walken , Mia Farrow and Selma Blair are joining Jordan Gelber in " Dark Horse ," the latest indie drama from Todd Solondz. The film centers on a thirtysomething man ( Gelber ) in arrested development who lives with his parents ( Walken and Farrow ), reluctantly works for his father and avidly collects toys. He seeks out a thirtysomething woman ( Blair ) in arrested development in an attempt to shed the "dark horse" status in his family and finally accomplish something. Aasif Mandvi, a correspondent for "The Daily Show With Jon Stewart" who appeared in "The Last Airbender," also is in the movie, playing Blair's "not quite" ex-boyfriend. Already cast are Justin Bartha ("The Hangover") as Gelber's more successful brother, Zachary Booth ("Nick and Nora's Infinite Playlist") as Gelber's easygoing cousin and Donna Murphy (