Michael Fassbender has joined Brendan Gleeson's directorial debut, At Swim-Two-Birds. The actor joins an Irish cast that already includes Colin Farrell, Cillian Murphy, Gabriel Byrne & Gleeson, as well as Gleeson's son, Domhnall. The film is an adaptation of Irish author Flann O'Brien's 1939 seminal metaphysical novel, a period drama about a 19-year-old student who sees the fictional characters in the play he's writing intertwining with the people in his life. ScreenDaily broke the news. Gleeson acquired the rights to the film seven years ago and has been developing it for four years. Fassbender is currently filming Ridley Scott's Prometheus.