I like the idea of slipstream as a film genre. Slipstream is usually applied to fiction, and is when a story isn't quite a fantasy or science fiction, but isn't really set in reality either. It might also be confused with magical realism, although that is a different genre altogether. I think most films that could possibly fall into this are classified in a sci fi film genre. Although I'm thinking of Stranger Than Fiction, which is called a comedy-drama most of the time, but I think could be called slipstream.