Real-life sisters Kate and Rooney Mara are to play twin sisters in the movie 'Bucking Fastard.'
The film is based on the true story of inseparable twin sisters Joan and Jean, who live on the edge of society.

The real-life actress sisters will play sex-crazed twins, inspired by 'British twins Freda and Greta Chaplin,' who gained attention in 1980 after it was revealed that the twins have uncontrollable sexual desires, and they were lusting over their next-door neighbor.
The twins claimed that they have one brain and can read each other's thoughts; they dress the same and live the same.
It is interesting that the real-life sisters Kate Mara and Rooney Mara have said yes to a movie like this because it looks like there will be sex, nudity, and potential lesbian incest in this.

Both sisters have done nudity in their past projects, so it wouldn't be a big deal for them to get naked again, but being intimate while your sister watches or engages in sexual acts with you is just another kind of hotness.

You should know that I am just guessing about the sexual content in this; the movie hasn't even started to film yet, and it is possible that there's no actual nudity in this and the movie is just a depressing story of two sisters.