Robert De Niro and Diane Keaton Say I Do To Indie Comedy BIG WEDDING May 13, 2011 Katherine Heigl and Amanda Seyfried to co-star. Robert De Niro and Diane Keaton will lead Justin Zackham’s indie comedy ‘Big Wedding,’ with Katherine Heigl and Amanda Seyfried also set to star. De Niro and Keaton play Don and Ellie Griffin a long divorced couple who, for the sake of their adopted son’s upcoming nuptials and his biological mother, pretend they are still married. It doesn’t take long for them to discover that acting the part isn’t easy, especially when their past, present and future unravel for all to see. Zackham (‘Lights Out,’ ‘The Bucket List’) will direct from his own screenplay.