The filming of Memento took only 25 days.

In the scene where Lenny is on the phone describing how Sammy Jenkis ends up in a home due to the death of his wife, it shows Sammy sitting in a chair looking towards the camera. Sammy is temporarily blocked from our view by someone walking in front of him. As the person passes by, it is not Sammy that re-appears, but Lenny. To see it well, you will have to use the frame-by-frame mode. There are about 5 visible frames of Lenny in the home, and then it cuts back to him inside the motel room talking on the phone again.

You can get some additional clues about the film on www.otnemem.com (memento spelled backwards). Included are some scraps of notes of Leonard's psychiatrist in the ward where he was kept.

The movie plays out in alternating color and black and white scenes. Chronologically, the black and white scenes are first, in the order they are in the movie, and the last black and white scene fades into color because it is perfectly continuous leading in to the color scenes.

You'll notice that throughout the film everyone calls Leonard "Lenny" even after he repeatedly tells them he hates it. The only time anyone calls him Leonard is when Natalie is trying to manipulate him into doing what she wants.