Lickerish Quartet

This is a 70's film with some weird stuff going on. The movie starts with this husband and wife watching adult films with their seemingly retarded son. When they're done there, they go to a carnival and see a motorcycle stuntwoman who they are convinced is one of the girls from the previously viewed films. They invite her home and the son performs a magic act before his parents can turn on the film. I'm not sure what they think will happen when the girl sees the film that she's in, but there's some sort of issue with the film and it's not the right episode or something. She spends the night, throws some books on the floor then strips naked to nail the husband. Except randomly, the screen goes to black and white and it's like it's wartime or they're in one of the films they're watching. Not sure what that's all about. Then the girl sleeps with everyone in the family. The next scene is the son and the motorcycle girl having the same conversation watching the same movie as his father. So some sort of endless cycle of weirdness. Not a recommender in my book.