Kate and Rooney Mara have spoken about starring together in Werner Herzog's new film Bucking Fastard, which premiered in competition at the Venice Film Festival to a six-and-a-half-minute standing ovation. The real-life sisters play Irish siblings who speak, think and move in unison, a demanding technical feat that required them to perform in perfect sync throughout the film; both actors said they had no reservations about working with Herzog despite his reputation for extreme behaviour on set, which he insists is media exaggeration.

In the film, the Mara sisters play Jean and Joan Holbrooke, twins who launch a campaign of arson and other misdemeanours after their former lover Gareth Mulroney, played by Orlando Bloom, marries someone else, eventually becoming tabloid figures assigned a social worker played by Domhnall Gleeson. The story is loosely based on Freda and Greta Chaplin, real-life identical twins from York who spoke in unison and gained tabloid notoriety following a 1981 court case. Herzog, known for films including Fitzcarraldo and Grizzly Man, said he wrote the screenplay in just five days once he settled on casting real sisters for the roles; HanWay Films is handling international sales.